These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Modification of poly(vinyltrimethylsilane) by radiation-induced graft polymerization  

NASA Astrophysics Data System (ADS)

The modification of polyvinyltrimethylsilane (PVTMS) has been carried out using the radiation-induced graft polymerization. PVTMS is applied as a basis for gas-separating membranes. Acrylonitrile, acrolein, ethyl acrylate, acrylic acid and acrylamide were used as monomers. The grafting was performed both from vapour and liquid phase of monomers and their solutions by the direct radiation method. Some kinetic regularities of radiation graft polymerization of monomers and the character of distribution of grafted polymers along the thickness of PVTMS films were studied. It was shown that grafting improves the chemical resistance, the selective permeability of gases and some mechanical properties of PVTMS films.

Kudryavtsev, Val. N.; Starannikova, L. E.; Teplyakov, V. V.; Kabanov, V. Ya.

1999-05-01

2

Antimicrobial fabric adsorbed iodine produced by radiation-induced graft polymerization  

NASA Astrophysics Data System (ADS)

Antimicrobial fabric was synthesized by radiation-induced graft polymerization of N-vinyl pyrrolidone onto polyolefine nonwoven fabric and subsequent adsorption of iodine. In response of the huge request for the antimicrobial material applied to face masks for swine flu in 2009, operation procedure of continuous radiation-induced graft polymerization apparatus was improved. The improved grafting production per week increased 3.8 times compared to the production by former operation procedure. Shipped antimicrobial fabric had reached 130,000 m2 from June until December, 2009.

Aoki, Shoji; Fujiwara, Kunio; Sugo, Takanobu; Suzuki, Koichi

2013-03-01

3

Advances in radiation grafting  

Microsoft Academic Search

Graft copolymerization is an attractive means for modifying base polymers because grafting frequently results in the superposition of properties relating to the backbone and pendent chains. Among the various methods for initiating the grafting reaction, ionizing radiation is the cleanest and most versatile method of grafting available. Ion-exchange membranes play an important role in modern technology, especially in separation and

El-Sayed A. Hegazy; H. A. AbdEl-Rehim; H. Kamal; K. A. Kandeel

2001-01-01

4

Simultaneous radiation induced graft polymerization of N-vinyl-2-pyrrolidone onto polypropylene non-woven fabric for improvement of blood compatibility  

NASA Astrophysics Data System (ADS)

In this study, N-vinyl-2-pyrrolidone (NVP) was grafted onto polypropylene non-woven fabric (PPNWF) through a simultaneous irradiation induced graft polymerization technique. Effect of the parameters of graft polymerization, i.e., monomer concentration, absorbed dose and dose rate, on the degree of grafting (DG) was investigated. The graft polymerization of NVP was confirmed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). A contact angle goniometry was used to test water contact angle (WCA) of original PPNWF and modified samples. The in vitro blood compatibility, including hemolysis, protein adsorption, platelet adhesion and activated partial thromboplastin time (APTT) of tested specimens, was evaluated. The results demonstrated that the hemocompatibility of PPNWF was improved via graft polymerization of NVP.

Li, Rong; Wang, Hengdong; Wang, Wenfeng; Ye, Yin

2013-07-01

5

A study of the kinetics of radiational graft polymerization of acrylic monomers on a butadiene-styrene thermoelastomer  

Microsoft Academic Search

1.The kinetics of radiochemical grafting of acrylonitrile and acrylic acid to a butadiene-styrene thermoelastomer have been studied by irradiating a material impregnated with the monomer; it has been shown that kinetic chain rupture in such systems is a monomolecular process.2.The rate constant for propagation of the graft polyacrylonitrile chain and the activation energy for grafting have been calculated, the values

V. F. Timofeeva; G. G. Ryabchikova; A. K. Pikaev; V. I. Spitsyn

1982-01-01

6

GRAFT POLYMERIZATION OF STYRENE MONOMER AND MIXED MONOMER OF STYRENE AND ACRYLONITRILE ON TO ACRYLONITRILE-BUTADIENE COPOLYMER  

Microsoft Academic Search

Graft polymerization of styrene monomer and a mixed monomer of styrene ; and acrylonitrile onto an actylonitrilebuthdiene copolymer was conducted by both ; radiation and a chemical catalyst method. In the experiments, the radiation ; method used a direct process by which gamma radation was applied to a uniform ; solution, and the catalyst method adopted a solution polymerization process

A. Takahashi; S. Kobayashi

1963-01-01

7

Supramolecular Polymerization from Polypeptide-Grafted Comb Polymers  

SciTech Connect

The helical and tubular structures self-assembled from proteins have inspired scientists to design synthetic building blocks that can be 'polymerized' into supramolecular polymers through coordinated noncovalent interactions. However, cooperative supramolecular polymerization from large, synthetic macromolecules remains a challenge because of the difficulty of controlling the structure and interactions of macromolecular monomers. Herein we report the synthesis of polypeptide-grafted comb polymers and the use of their tunable secondary interactions in solution to achieve controlled supramolecular polymerization. The resulting tubular supramolecular structures, with external diameters of hundreds of nanometers and lengths of tens of micrometers, are stable and resemble to some extent biological superstructures assembled from proteins. This study shows that highly specific intermolecular interactions between macromolecular monomers can enable the cooperative growth of supramolecular polymers. The general applicability of this strategy was demonstrated by carrying out supramolecular polymerization from gold nanoparticles grafted with the same polypeptides on the surface.

Wang, Jing [ORNL; Lu, Hua [ORNL; Kamat, Ranjan K [ORNL; Pingali, Sai Venkatesh [ORNL; Urban, Volker S [ORNL; Cheng, Jianjun [University of Illinois, Urbana-Champaign; Lin, Yao [ORNL

2011-01-01

8

Chemical Modification of Cellulose Nanofibrils by Graft Polymerization  

E-print Network

Chemical Modification of Cellulose Nanofibrils by Graft Polymerization Arie Mulyadi and Yulin Deng film shows strongly entangled fiber. Modified CNF film displays more porous network due to: Limited Funding for this project was provided by IPST Fellowship Cellulose Nanofibrils (CNF) Merits

Das, Suman

9

Emulsion graft polymerization of 4-chloromethylstyrene on kenaf fiber by pre-irradiation method  

NASA Astrophysics Data System (ADS)

The stability of micelle size in 3% 4-chloromethylstyrene (CMS), 0.3% Tween 20 in water emulsion over time was studied using a static light scattering. It was found that the micelle diameter decreased with storage time and temperature. The influence of micelle size over time was then explored by adjusting the ratio of CMS to Tween 20 (10:1, 10:2, 10:4) at CMS concentration of 0.2-5.0%. It was found that the increase in average micelle diameter resulted in a decreased in the stability of CMS emulsion. Graft polymerization of CMS on kenaf fiber was carried out in emulsion with 350 nm micelle at various CMS concentrations at a dose of 150 kGy. It was found that the degree of grafting (Dg) was strongly dependent on the monomer concentration and time. However, the increase in micelles diameter from 250 nm to 500 nm resulted in the increased in Dg from 3% to 153%. This extraordinary result led us to investigate the micelle size distributions of CMS emulsion during graft polymerization. It was found that the diameter of micelle decreased rapidly to 100 nm within 2 h. It was discovered from digital photomicrography the existence of multiple emulsions in the CMS emulsion. It was proposed that the enhancement of grafting yield is governed by emulsion breakdown mechanisms through radical effect during radiation induced graft polymerization.

Mohamed, Nor Hasimah; Tamada, Masao; Ueki, Yuji; Seko, Noriaki

2013-01-01

10

Gamma radiation grafted polymers for immobilization of Brucella antigen in diagnostic test studies  

NASA Astrophysics Data System (ADS)

The radiation grafting process has a wide field of industrial applications, and in the recent years the immobilization of biocomponents in grafted polymeric materials obtained by means of ionizing radiations is a new and important contribution to biotechnology. In the present work, gamma preirradiation grafting method was employed to produce acrylics hydrogels onto polyethylene (PE), polyvinyl chloride (PVC) and polystyrene (PS). Two monomers were used to graft the previously mentioned polymers: methacrylic acid (MAAc) and acrylamide (AAm), and several working conditions were considered as influencing the degree of grafting. All this grafted polymers were used to study the possibility of a subsequent immobilization of Brucella antigen (BAg) in diagnostic test studies (ELISA).

Docters, E. H.; Smolko, E. E.; Suarez, C. E.

11

Surface modification of polypropylene membrane by polyethylene glycol graft polymerization.  

PubMed

Polypropylene hollow fiber microporous membranes have been used in a wide range of applications, including blood oxygenator. The hydrophobic feature of the polypropylene surface causes membrane fouling. To minimize fouling, a modification consisting of three steps: surface activation in H2 and O2 plasma, membrane immersion in polyethylene glycol (PEG) and plasma graft polymerization was performed. The membranes were characterized by contact angle measurement, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), tensile test, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Oxygen transfer of modified membranes was also tested. The stability of grafted PEG was measured in water and in phosphate buffer saline (PBS) at 37°C. Blood compatibility of modified surfaces was evaluated by the platelet adhesion method. Water contact angel reduction from 110° to 72° demonstrates the enhanced hydrophilicity, and XPS results verify the presence of oxygenated functional groups due to the peak existence in 286 eV as a result of PEG grafting. The results clearly indicate that plasma graft-polymerization of PEG is an effective way for antifouling improvement of polypropylene membranes. Also, the results show that oxygen transfer changes in PEG grafted membranes are not significant. PMID:25063140

Abednejad, Atiye Sadat; Amoabediny, Ghasem; Ghaee, Azadeh

2014-09-01

12

Durable Nanolayer Graft Polymerization of Functional Finishes Using Atmospheric Plasma  

NASA Astrophysics Data System (ADS)

Various applications of atmospheric pressure plasma were investigated in conjunction with different chemistries on nonwoven materials including spunbond polyester (PET) and spunbod polypropylene for fuel separation and antimicrobial functionalities. Hydrophobic/Oleophobic properties were conferred on nonwoven polyester (PET) via plasma-induced graft polymerization of different hydrophobic non-C8 perfluorocarbon chemistry including perfluorohexylethylmethacrylate, perfluorohexylethylacrylate, allylpentafluorobenzene, pentafluorostyrene, or 1,3-divinyltetramethyldisiloxane in the vapor form using both in-situ and down-stream plasma configurations. Different nanolayers of the grafted polymer were furnished on nonwovens to generate surfaces with different level of wettabilities for medical applications and water/fuel separation. The effect of various hydrophobic chemistry, different plasma conditions, and plasma device parameters including plasma power and plasma exposure time were studied and the performance was characterized by measuring the contact angle and the wettability rating against liquids with broad range of surface tensions. Vapor deposition of 2-(perfluorohexyl)ethyl methacrylate and pentafluorostyrene on nonwoven PET followed by plasma-induced graft polymerization was investigated for possible use in water/fuel separation. Different nanolayer thicknesses (80-180nm) of the grafted polymer were achieved to generate surfaces with different wettabilities for water/fuel separation of different fuel compositions. The effect of different plasma conditions and device parameters including the flow rate of monomers, power of the device, and time of plasma exposure on the separation of different fuels was studied and characterized by measuring the surface energy of the treated substrates. The surface chemistry and morphology of the treated samples were characterized using XPS, SEM and TOF-SIMS techniques which confirmed the grafting of monomer onto the substrate. Furthermore, spunbond nonwoven polypropylene fabric, commonly used for hygienic products, was treated with diallyldimethylammonium chloride (DADMAC). Atmospheric pressure glow discharge plasma was used to induce free radical chain polymerization of the ADMAC monomer, which conferred a graft polymerized network on the fabric with durable antimicrobial properties. The effect of different DADMAC concentration, and plasma conditions including the RF power and the time of plasma exposure were studied and the optimum treatment conditions were identified by calculating the surface charge density on the treated fabrics. The presence of poly-DADMAC on the polypropylene surface was confirmed using SEM, FT-IR and TOF-SIMS. Antibacterial performance was investigated using standard test methods (AATCC TM 100) for both gram positive and gram negative bacteria. The antimicrobial results showed 6 log reductions in the bacterial activities of K. pneumoniae and S .aureus, which was unprecedented using a plasma-induced graft polymerization approach.

Mazloumpour, Maryam

13

Radiation-hardened polymeric films  

SciTech Connect

This patent describes polymeric dielectric compositions with reduced radiation induced conductivity, containing from about 10/sup 15/ to 10/sup 21/ molecules/cm/sup 3/ of a compatible organic Lewis acid or Lewis base as dopant. The dielectric is a low electronic mobility polymer selected from the group consisting of polyesters, polyolefins, perfluorinated polyolefins, vinyl polymers, vinylidene polymers, polycarbonates, polysulfones, and polyimides.

Arnold, C. Jr.; Hughes, R.C.; Kepler, G.; Kurtz, S.R.

1986-11-11

14

Graft polymerization of methacrylic acid on starch and hydrolyzed starches  

Microsoft Academic Search

Hydrolysis of maize starch with HCl was studied under various conditions with a view to obtaining starches having different molecular sizes. To this end, the original starches and hydrolyzed starches derived from them were indepen-dently graft-copolymerized with methacrylic acid (MAA) using KMnO4\\/citric acid as initiator. Thus the molecular weight of the polymeric backbone of starch and the substituents present on

Kh. M. Mostafa

1995-01-01

15

Impact of solvent selection on graft polymerization of acrylamide onto starch  

Technology Transfer Automated Retrieval System (TEKTRAN)

The impact on polymer properties (Mn, monomer conversion, graft content, graft efficiency and anhydroglucose units between grafts) that result from changing the solvent for the graft polymerization of acrylamide onto starch from water to dimethylsulfoxide (DMSO) was evaluated. Reaction conditions we...

16

Studies on the graft polymerizations of styrene and methyl methacrylate to hydroxyl terminated polybutadiene  

Microsoft Academic Search

Hydroxyl terminated Polybutadiene (HTPB) was grafted with styrene (St) or methyl methacrylate (MMA) by free radical solution polymerization. The graft copolymerizations were conducted in benzene at 70 °C. The initiators used were benzoyl peroxide (BPO) and azobis-isobutyronitrile (AIBN). The microstructures of theobtained graft copolymers were characterized by13C NMR measurement and the DEPT technique, as well as by IR spectrometer. The

Chang-Tay Lin; Mon-Chun Liu

1995-01-01

17

Radiation grafting on natural films  

NASA Astrophysics Data System (ADS)

Different methods of polymer grafting using gamma irradiation are reported in the present study for the preparation of newly functionalized biodegradable films, and some important properties related to their mechanical and barrier properties are described. Biodegradable films composed of zein and poly(vinyl alcohol) (PVA) were gamma-irradiated in presence of different ratios of acrylic acid (AAc) monomer for compatibilization purpose. Resulting grafted films (zein/PVA-g-AAc) had their puncture strength (PS=37-40 N mm-1) and puncture deformation (PD=6.5-9.8 mm) improved for 30% and 50% PVA in blend, with 5% AAc under 20 kGy. Methylcellulose (MC)-based films were irradiated in the presence of 2-hydroxyethyl methacrylate (HEMA) or silane, in order to determine the effect of monomer grafting on the mechanical properties of films. It was found that grafted films (MC-g-HEMA and MC-g-silane) using 35% monomer performed higher mechanical properties with PS values of 282-296 N mm-1 and PD of 5.0-5.5 mm under 10 kGy. Compatibilized polycaprolactone (PCL)/chitosan composites were developed via grafting silane in chitosan films. Resulting trilayer grafted composite film (PCL/chitosan-g-silane/PCL) presented superior tensile strength (TS=22 MPa) via possible improvement of interfacial adhesion (PCL/chitosan) when using 25% silane under 10 kGy. Finally, MC-based films containing crystalline nanocellulose (CNC) as a filling agent were prepared and irradiated in presence of trimethylolpropane trimethacrylate (TMPTMA) as a grafted plasticizer. Grafted films (MC-g-TMPTMA) presented superior mechanical properties with a TS of 47.9 MPa and a tensile modulus (TM) of 1792 MPa, possibly due to high yield formation of radicals to promote TMPTMA grafting during irradiation. The addition of CNC led to an additional improvement of the barrier properties, with a significant 25% reduction of water vapor permeability (WVP) of grafted films.

Lacroix, M.; Khan, R.; Senna, M.; Sharmin, N.; Salmieri, S.; Safrany, A.

2014-01-01

18

Surface modification of ultra high molecular weight polyethylene fibers via the sequential photoinduced graft polymerization  

NASA Astrophysics Data System (ADS)

In this study, a sequential photoinduced graft polymerization process was proposed to improve the poor interfacial bonding property of ultra high molecular weight polyethylene (UHMWPE) fibers. The polymerization was initiated by dormant semipinacol (SP) groups and carried out in a thin liquid layer. Methacrylic acid (MAA) and acryl amide (AM) were grafted stepwise onto the surface of UHMWPE fibers. Attenuated total reflectance infrared spectroscopy (ATR-IR) and thermo gravimetric analysis (TGA) confirmed the grafting. The analysis result of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) indicated the structure of grafted chains. Scanning electron microscopy (SEM) images and atomic force microscopy (AFM) images revealed the apparent morphology changing, and the grafted layers were observed. Interfacial shear stress (IFSS) test of the modified fibers showed an extensively improved interfacial bonding property. The active groups grafted onto the fibers would supply enough anchor points for the chemical bonding with various resins or further reactions.

Li, Zhi; Zhang, Wei; Wang, Xinwei; Mai, Yongyi; Zhang, Yumei

2011-06-01

19

The synthesis of well-defined poly(vinylbenzyl chloride)-grafted nanoparticles via RAFT polymerization  

PubMed Central

Summary We describe the use of one of the most advanced radical polymerization techniques, the reversible addition fragmentation chain transfer (RAFT) process, to produce highly functional core–shell particles based on a silica core and a shell made of functional polymeric chains with very well controlled structure. The versatility of RAFT polymerization is illustrated by the control of the polymerization of vinylbenzyl chloride (VBC), a highly functional monomer, with the aim of designing silica core–poly(VBC) shell nanoparticles. Optimal conditions for the control of VBC polymerization by RAFT are first established, followed by the use of the “grafting from” method to yield polymeric brushes that form a well-defined shell surrounding the silica core. We obtain particles that are monodisperse in size, and we demonstrate that the exceptional control over their dimensions is achieved by careful tailoring the conditions of the radical polymerization. PMID:23843918

Moraes, John; Ohno, Kohji; Gody, Guillaume; Maschmeyer, Thomas

2013-01-01

20

Comparison of surface modifications of poly(ether urethanes) by chemical infusion and graft polymerization  

SciTech Connect

Our approach to surface modification uses the chemical infusion process to introduce materials into the outermost layer of the polymeric material, thereby altering the surface without changing the bulk properties of the polymer. The infused materials may slowly diffuse out of the infusion layer if they are volatile or highly mobile. However, if polymeric infusant materials are employed, they may become chain entangled with the host polymer and result in a permanently modified surface. A second approach utilizes photo-initiated graft polymerization of poly(ether urethanes) with an appropriate monomer. We have explored both of these methods by examining the infusion of polyvinylpyrrolidone (PVP) and poly(ethylene glycol) (PEG) into commercially available poly(ether urethanes) and the graft polymerization of N-vinyl pyrrolidone onto poly(ether urethanes). Results are presented here. 7 refs., 1 tab.

Wrobleski, D.A.; Cash, D.L.; Hermes, R.E.

1988-01-01

21

Technique of radiation polymerization in fine art conservation: a potentially new method of restoration and preservation. [Uv and electron beams  

SciTech Connect

The technique of using radiation polymerization for the restoration and preservation of art treasures is considered. The processes discussed include both radiation grafting and rapid cure procedures, particularly reactions initiated by uv and eb. Representative examples where the technique has already been used are treated including typical applications with paintings, tapestries, leather and archival repair. The structure of the monomers and oligomers used in both grafting and rapid cure systems is outlined. The experimental conditions where grafting may occur during radiation rapid cure processing are discussed. Possible future developments of the technique are outlined. 1 figure, 8 tables.

Garnett, J.L. (Univ. of New South Wales, Kensington, Australia); Major, G.

1982-01-01

22

Technique of radiation polymerization in fine art conservation: a potentially new method of restoration and preservation. [Uv and electron beams  

Microsoft Academic Search

The technique of using radiation polymerization for the restoration and preservation of art treasures is considered. The processes discussed include both radiation grafting and rapid cure procedures, particularly reactions initiated by uv and eb. Representative examples where the technique has already been used are treated including typical applications with paintings, tapestries, leather and archival repair. The structure of the monomers

J. L. Garnett; G. Major

1982-01-01

23

Radiation-induced grafting of chlorinated PVC for preparation of plastic foams  

NASA Astrophysics Data System (ADS)

Graft products of chlorinated PVC with styrene were prepared by a radiation-grafting method using 60Co- ?-ray source. The aim was the preparation of foamed plastics by applying the traditional polystyrene foaming method. Two types of chlorinated PVC (PVCC) were used: radiation-chlorinated PVC, made by the fluidized-bed chlorination process, and solution-chlorinated PVC. Both of the PVCC types were grafted with styrene without any difficulty. The required particle size for an effective foaming was obtained by extrusion and granulation of the grafted powder. The foaming processes are quite different: graft products on the basis of solution-chlorinated PVC lead to plastic foams with a density lower than 0.1 g/cm 3 whereas those prepared from solid-chlorinated PVC result in foams with much higher density (Friese, K, Tannert, F, 1990. Proceedings of the 7th Tihany Symposium on Radiation Chemistry, p. 367). Solid-chlorinated PVC is foamable with pentane, after compounding it with polymeric modifiers. Grafting of granules on the basis of such compounds increases the content of pentane, as well as the foaming rate. The foamed graft polymers are non-inflammable and self-extinguishing.

Friese, K.; Tannert, F.

1999-06-01

24

Argon Plasma-Induced Graft Polymerization of PEGMA on Chitosan Membrane Surface for Cell Adhesion Improvement  

NASA Astrophysics Data System (ADS)

For its biocompatibility and biodegradability, chitosan has had considerable attention for biomedical applications in recent years. In this paper, polymerization of poly (ethylene glycol) methyl ether methacrylate (PEGMA) was grafted onto chitosan membrane surface through argon plasma-induced graft polymerization. The surface properties after modification were characterized by contact angle measurement, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The results indicated that PEGMA can be grafted successfully onto chitosan membrane surface. The surface hydrophilicity and free energy were improved and the surface roughness increased after modification. The adhesion of a human corneal epithelial cell (HCEC) on chitosan membrane surface was enhanced due to improvement of surface free energy and roughness.

Yin, Shiheng; Ren, Li; Wang, Yingjun

2013-10-01

25

R&D for graft adsorbents by radiation processing  

NASA Astrophysics Data System (ADS)

Fibrous adsorbent for removal and recovery of metal ions have been synthesized by graft polymerization. In the grafting, the functional groups which have high selectivity against for target metal ions such as Fe, Sc, As, and U are introduced onto nonwoven fabric. When the monomer has a chelate group which makes selective coordination bond to specific these ions, it was directly grafted on the trunk polymer. In the case of precursor monomer having functional groups such as epoxy ring, the grafted trunk fabric is chemically modified. The resultant fibrous adsorbent leads the swift adsorption of metal ions. This property by using fibrous material can reduce the column size of adsorbent in the purification of waste water. The size of purification equipment becomes quite compact and that implies total volume of equipment can reduce. Instead of organic solvent, emulsion system which disperses monomer micelles in water with assistance of surfactant was found to accelerate the graft polymerization. This means the air pollution from organic solvent can be avoided by water system grafting. Furthermore, since the emulsion grafting was highly efficient, the required irradiation dose was considerably lower compared to general organic solvent system. As a result, the emulsion grafting has enormous potential for natural polymer to use as a trunk material for grafting. If a natural polymer such as cellulose can be used, the dependence on petroleum resources, the amount of industrial waste and the generation of carbon dioxide will be reduced to some extent.

Seko, Noriaki; Tamada, Masao

26

Immobilization of peroxidase on SPEU film via radiation grafting  

NASA Astrophysics Data System (ADS)

The acrylic acid or acrylamide were grafted via radiation onto segmented polyetherurethane (SPEU) film which is a kind of biocompatible material. Then the Horse radish peroxidase was immobilized on the grafted SPEU film through chemical binding. Some quantitative relationships between the percent graft and the activity, amount of immobilized enzyme were given. The properties and application of obtained biomaterial was studied as well.

Hongfei, Ha; Guanghui, Wang; Jilan, Wu

27

A short review of radiation-induced raft-mediated graft copolymerization: A powerful combination for modifying the surface properties of polymers in a controlled manner  

NASA Astrophysics Data System (ADS)

Surface grafting of polymeric materials is attracting increasing attention as it enables the preparation of new materials from known and commercially available polymers having desirable bulk properties such as thermal stability, elasticity, permeability, etc., in conjunction with advantageous newly tailored surface properties such as biocompatibility, biomimicry, adhesion, etc. Ionizing radiation, particularly ? radiation is one of the most powerful tools for preparing graft copolymers as it generates radicals on most substrates. With the advent of living free-radical polymerization techniques, application of ? radiation has been extended to a new era of grafting; grafting in a controlled manner to achieve surfaces with tailored and well-defined properties. This report presents the current use of ? radiation in living free-radical polymerization and highlights the use of both techniques together as a combination to present an advance in the ability to prepare surfaces with desired, tunable and well-defined properties.

Barsbay, Murat; Güven, Olgun

2009-12-01

28

Grafting of molecularly imprinted polymer to porous polyethylene filtration membranes by plasma polymerization.  

PubMed

An application of plasma-induced grafting of polyethylene membranes with a thin layer of molecularly imprinted polymer (MIP) was presented. High-density polyethylene (HDPE) membranes, "Vyon," were used as a substrate for plasma grafting modification. The herbicide atrazine, one of the most popular targets of the molecular imprinting, was chosen as a template. The parameters of the plasma treatment were optimized in order to achieve a good balance between polymerization and ablation processes. Modified HDPE membranes were characterized, and the presence of the grafted polymeric layer was confirmed based on the observed weight gain, pore size measurements, and infrared spectrometry. Since there was no significant change in the porosity of the modified membranes, it was assumed that only a thin layer of the polymer was introduced on the surface. The experiments on the re-binding of the template atrazine to the membranes modified with MIP and blank polymers were performed. HDPE membranes which were grafted with polymer using continuous plasma polymerization demonstrated the best result which was expressed in an imprinted factor equal to 3, suggesting that molecular imprinting was successfully achieved. PMID:23748644

Cowieson, D; Piletska, E; Moczko, E; Piletsky, S

2013-08-01

29

The effects of early postoperative radiation on vascularized bone grafts  

SciTech Connect

The effects of early postoperative radiation were assessed in free nonvascularized and free vascularized rib grafts in the canine model. The mandibles of one-half of the dogs were exposed to a cobalt 60 radiation dose of 4080 cGy over a 4-week period, starting 2 weeks postoperatively. The patency of vascularized grafts was confirmed with bone scintigraphy. Histological studies, including ultraviolet microscopy with trifluorochrome labeling, and histomorphometric analyses were performed. Osteocytes persist within the cortex of the vascularized nonradiated grafts to a much greater extent than in nonvascularized, nonradiated grafts. Cortical osteocytes do not persist in either vascularized or nonvascularized grafts subjected to radiation. New bone formation is significantly retarded in radiated grafts compared with nonradiated grafts. Periosteum and endosteum remained viable in the radiated vascularized grafts, producing both bone union and increased bone turnover, neither of which were evident to any significant extent in nonvascularized grafts. Bone union was achieved in vascularized and non-vascularized nonradiated bone. In the radiated group of dogs, union was only seen in the vascularized bone grafts.

Evans, H.B.; Brown, S.; Hurst, L.N. (Division of Plastic and Reconstructive Surgery, University of Western Ontario, London (Canada))

1991-06-01

30

Reduced platelets and bacteria adhesion on poly(ether ether ketone) by photoinduced and self-initiated graft polymerization of 2-methacryloyloxyethyl phosphorylcholine.  

PubMed

Aromatic poly(ether ether ketone) (PEEK) is a super engineering plastic, which has good mechanical properties and is resistant to physical and chemical stimuli. We have, therefore, attempted to use PEEK in cardiovascular devices. Synthetic cardiovascular devices require both high hemocompatibility and anti-inflammatory activity in addition to the mechanical properties. We modified the PEEK surface by photoinduced and self-initiated graft polymerization with 2-methacryloyloxyethyl phosphorylcholine (MPC; PMPC-grafted PEEK) for obtaining good antithrombogenicity. Polymerization was carried out on the surface of PEEK under radiation of ultraviolet (UV) light during which we controlled monomer concentrations, temperatures, and UV intensities. The biological performance of the PMPC-grafted PEEK was examined and compared with that of unmodified PEEK. With increase in the thickness of the PMPC layer, the amount of fibrinogen adsorption decreased significantly in comparison to that in the case of unmodified PEEK. When placed in contact with human platelet-rich plasma, surface of the PMPC-grafted PEEK clearly showed inhibition of platelet adhesion and activation. Also, bacterial adhesion was reduced dramatically on the PMPC-grafted PEEK. Thus, the PMPC grafting on PEEK improved the antithrombogenicity. PMID:23720384

Tateishi, Takaharu; Kyomoto, Masayuki; Kakinoki, Sachiro; Yamaoka, Tetsuji; Ishihara, Kazuhiko

2014-05-01

31

Characterization of Electroinitiated and Radiation Polymerized Poly(Butadiene Sulfone)  

Microsoft Academic Search

Polymerization of butadiene sulfone was accomplished by using two different methods. The first method involves electrochemical polymerization of the monomer using the constant potential electrolysis technique. Oxidation of the monomer under nitrogen atmosphere in an acetonitrile-tetrabutylammonium tetrafluoroborate system yields brown, tarry polymers. On the other hand, the second initiation method, which was radiation polymerization, yields white, powdery polymers. Structural analyses

B. Hacioglu; S. Suzer; U. Akbulut; L. Toppare; P. Aybar; J. H. P. Utley

1991-01-01

32

Surface Modification of Materials by Plasma Process and UV-induced Grafted Polymerization for Biomedical Applications  

NASA Astrophysics Data System (ADS)

Surface modification using plasma treated and graft polymerization is versatile process, with systems on the market capable of treating everything from polymer, metal, and ceramic substrates. The major advantage is that the modification is caused no substrate damage or bulk property changes. This is a very effective method to modify the surfaces of biomaterials to achieve desired physical or mechanical properties, or to induce a specific response when the device is placed in the body. They offer attractive possibilities for developing new biomaterials and for improving the performance of existing materials and devices. Hence, in this review, we describe the application of plasma treatment and graft polymerization on biomaterials field. The various applications are discussed in the following: (1) easy stripped-off wound dressing, (2) porous three-dimensional temporary scaffolds, (3) quartz crystal microbalance (QCM) base biosensors, and (4) covalent immobilization of glucose oxidase onto inorganic substrates

Chen, Ko-Shao; Chen, Su-Chen; Lien, Wei-Cheng; Tsai, Jui-Che; Ku, Yuan-An; Lin, Hong-Ru; Lin, Feng-Huei; Wu, Te-Hsing; Chen, Chia-Chieh; Chen, Tim-Mo; Chiou, Shih-Hwa

33

Plasma polymerized thin coating as a protective layer of carbon nanotubes grafted on carbon fibers  

NASA Astrophysics Data System (ADS)

Nanoparticles addition is widely studied to improve properties of carbon fiber reinforced composites. Here, hybrid carbon fiber results from grafting of carbon nanotubes (CNT) by Chemical Vapor Deposition (CVD) on the carbon fiber for mechanical reinforcement and conductive properties. Both tows and woven fabrics made of the hybrid fibers are added to the matrix for composite processing. However handling hybrid fibers may induce unwilling health risk due to eventual CNT release and a protective layer is required. A thin coating layer is deposited homogeneously by low pressure plasma polymerization of an organic monomer without modifying the morphology and the organization of grafted CNTs. The polymeric layer effect on the electrical behavior of hybrid fiber is assessed by conductivity measurements. Its influence on the mechanical properties is also studied regarding the interface adhesion between fiber and matrix. The protective role of layer is demonstrated by means of friction constraints applied to the hybrid fiber.

Einig, A.; Rumeau, P.; Desrousseaux, S.; Magga, Y.; Bai, J. B.

2013-04-01

34

Enhanced microwave absorption performance of polyaniline-coated CNT hybrids by plasma-induced graft polymerization  

NASA Astrophysics Data System (ADS)

Highly conducting CNT/polyaniline hybrids were prepared by plasma-induced graft polymerization, i.e., plasma pretreatment of CNTs and further in situ polymerization of aniline. Plasma pretreatment made more aniline grafted on the CNTs' surface by the role of oxygen radicals. SEM images showed that the surfaces of CNTs were uniformly coated by PANI. FTIR showed that there was presence of strong interaction between CNTs and PANI molecular chains. The conductivity of CNT/PANI hybrids with plasma treatment is higher than that of CNT/PANI hybrids without plasma pretreatment (0.443 S/cm at 0 W) or pretreated by acid oxidation method. Importantly, the microwave absorption properties were investigated by measuring complex permeability, complex permittivity and reflection loss in a frequency of 2-18 GHz. The microwave absorption enhancement of CNT/PANI hybrids results mainly from dielectric loss rather than magnetic loss due to higher value of dielectric loss.

Cheng, Junye; Zhao, Bin; Zheng, Shiyou; Yang, Junhe; Zhang, Deqing; Cao, Maosheng

2015-01-01

35

Surface modification of microfluidic channels by UV-mediated graft polymerization of non-fouling and ‘smart’ polymers  

NASA Astrophysics Data System (ADS)

Microfluidic channels prepared from polydimethylsiloxane (PDMS) have been modified by UV-mediated graft polymerization of temperature-responsive polymers (poly[ N-isopropyl acrylamide] or pNIPAAm), temperature- and pH-responsive copolymers (P[NIPAAm-co-acrylic acid (AAc)]), and a non-fouling hydrogel (polyethyleneglycol diacrylate, or PEGDA). This was done by presorbing a photosensitizer (PS) within the PDMS channel surface regions, contacting the different monomer solutions with the PS-containing surface under nitrogen, and irradiating with UV. The pNIPAAm-grafted surface was hydrophilic below its lower critical solution temperature (LCST), resisting non-specific adsorption, while it was hydrophobic above its LCST, now binding pNIPAAm-coated nanoparticles. Combined temperature- and pH-responsive surfaces were also prepared by UV radiation grafting a monomer mixture of pNIPAAm with AAc. The surfaces have been characterized by advancing water contact angle measurements. These smart microfluidic channels should be useful for many applications such as affinity separations and diagnostic assays.

Ebara, Mitsuhiro; Hoffman, John M.; Stayton, Patrick S.; Hoffman, Allan S.

2007-08-01

36

Polyglycerol dendrimers immobilized on radiation grafted poly-HEMA hydrogels: Surface chemistry characterization and cell adhesion  

NASA Astrophysics Data System (ADS)

Radiation induced grafting of poly(2-hydroxyethylmethacrylate) (PHEMA) on low density polyethylene (LDPE) films and subsequent immobilization of poly(glycerol) dendrimer (PGLD) has been performed with the aim to improve cell adhesion and proliferation on the surface of the polymer, in order to enhance their properties for bone tissue engineering scaffolding applications. Radiation grafting of PHEMA onto LDPE was promoted by ?-ray radiation. The covalent immobilization of PGLD on LDPE-g-PHEMA surface was performed by using a dicyclohexyl carbodiimide (DCC)/N,N-dimethylaminopyridine (DMAP) method. The occurrence of grafting polymerization of PHEMA and further immobilization of PGLD was quantitatively confirmed by photoelectron spectroscopy (XPS) and fluorescence, respectively. The LDPE-g-PHEMA surface topography after PGLD coupling was studied by atomic force microscopy (AFM). The hydrophilicity of the LDPE-g-PHEMA film was remarkably improved compared to that of the ungrafted LDPE. The core level XPS ESCA spectrum of PHEMA-grafted LDPE showed two strong peaks at 286.6 eV (from hydroxyl groups and ester groups) and 289.1 eV (from ester groups) due to PHEMA brushes grafted onto LDPE surfaces. The results from the cell adhesion studies show that MCT3-E1 cells tended to spread more slowly on the LDPE-g-PHEMA than on the LDPE-g-PHEMA-i-PGLD.

Higa, Olga Z.; Faria, Henrique Antonio Mendonça; de Queiroz, Alvaro A. A.

2014-05-01

37

Nanocomposites of polystyrene/polystyrene-grafted graphene oxides synthesized by in-situ bulk polymerization.  

PubMed

In this study, polystyrene-grafted graphene oxide (GO-g-PS) nanocomposites with different PS chain lengths were prepared by in-situ polymerization, and their reinforcing effect on the PS matrix was investigated. The glass transition (T(g)) and the thermal degradation (T(d)) temperatures of the PS/GO-g-PS nanocomposites were increased up to 2.8 degrees C and 23.9 degrees C, respectively. The addition of only 0.1 wt% of the GO-g-PS to the PS/GO-g-PS nanocomposites increased the tensile strength and Young's modulus by around 20.5% and 71.4%, respectively. These results showed that the thermal and mechanical properties of the PS/GO-g-PS nanocomposites gradually improved with increasing length of the PS chain grafted onto the GO surface. These differences in reinforcing effects were attributed to differences in interfacial interaction between the graphene and PS matrix. PMID:23755588

Lee, Jaehoon; Yun, Young Soo; Kim, Do Hyeong; Park, Hyun Ho; Jin, Hyoung-Joon

2013-03-01

38

Temperature-sensitive hydrogels by graft polymerization of chitosan and N-isopropylacrylamide for drug release.  

PubMed

Thermo-responsive polysaccharidic hydrogels were designed and synthesized by a free radical induced grafting procedure. Chitosan was chosen as biopolymer to impart biocompatibility and biodegradability to the macromolecular systems, while N-isopropylacrylamide (NIPAAm) was selected as co-monomer responsive for the thermo-sensitive properties. Ammonium persulfate was the initiator system and different polymeric networks have been synthesized by modulating the amount of NIPAAm in the polymerization feed. The resulting hydrogels were proposed as drug delivery devices and their performance was evaluated by using Diclofenac sodium salt as a model drug. Hydrogels were carefully characterized by FT-IR spectrophotometry, calorimetric analyses and swelling behavior in a temperature range of 15-45°C. Finally, to verify the suitability of these hydrogels as thermo-responsive devices, the drug release profiles were studied performing in vitro experiments around the swelling-shrinking transition temperatures of the macromolecular systems. PMID:22200242

Spizzirri, Umile Gianfranco; Iemma, Francesca; Cirillo, Giuseppe; Altimari, Ilaria; Puoci, Francesco; Picci, Nevio

2013-01-01

39

EUV lithographic radiation grafting of thermo-responsive hydrogel nanostructures  

Microsoft Academic Search

Nanostructures of the thermoresponsive poly(N-isopropyl acrylamide) (PNIPAAm) and of PNIPAAm-block-poly(acrylic acid) copolymers were produced on poly(tetrafluoroethylene-co-ethyelene) (ETFE) films using extreme ultraviolet (EUV) lithographic exposure with subsequent graft-polymerization. The phase transition of PNIPAAm nanostructures at the low critical solution temperature (LCST) at 32°C was imaged by atomic force microscopy (AFM) phase contrast measurements in pure water. Results show a higher phase

Patrick Farquet; Celestino Padeste; Harun H. Solak; Selmiye Alkan Gürsel; Günther G. Scherer; Alexander Wokaun

2007-01-01

40

Surface modification of commercial aromatic polyamide reverse osmosis membranes by graft polymerization of 3-allyl-5,5-dimethylhydantoin  

Microsoft Academic Search

A commercially available aromatic polyamide reverse osmosis (RO) membrane was chemically modified to improve its chlorine resistance and anti-biofouling property. The raw RO membranes were modified by free-radical graft polymerization of 3-allyl-5,5-dimethylhydantoin (ADMH) using 2,2?-azobis(isobutyramidine) dihydrochloride as an initiator. Attenuated total reflective Fourier transform infrared spectra (ATR-FTIR) verified the successful graft of ADMH on the raw membrane surfaces. It was

Xinyu Wei; Zhi Wang; Zhe Zhang; Jixiao Wang; Shichang Wang

2010-01-01

41

Halloysite nanotubes grafted hyperbranched (co)polymers via surface-initiated self-condensing vinyl (co)polymerization  

Microsoft Academic Search

Halloysite nanotubes (HNTs) grafted hyperbranched polymers were prepared by the self-condensing vinyl polymerization (SCVP)\\u000a of 2-((bromoacetyl)oxy)ethyl acrylate (BAEA) and the self-condensing vinyl copolymerization of n-butyl acrylate (BA) and BAEA with BAEA as inimer (AB*) respectively, from the surfaces of the 2-bromoisobutyric acid modified\\u000a halloysite nanotubes (HNTs-Br) via atom transfer radical polymerization (ATRP) technique. The halloysite nanotubes grafted\\u000a hyperbranched polymer (HNTs-HP)

Bin Mu; Mingfei Zhao; Peng Liu

2008-01-01

42

Homogeneous ring opening graft polymerization of ?-caprolactone onto xylan in dual polar aprotic solvents.  

PubMed

Homogeneous ring-opening graft polymerization (ROGP) of ?-caprolactone (?-CL) onto xylan was investigated in dual polar aprotic solvents, N,N-dimethylformamide/lithium chloride (DMF/LiCl), N,N-dimethylacetamide/LiCl (DMAc/LiCl), and 1-methyl-2-pyrrolidinone/LiCl (NMP/LiCl). The effects of reaction solvents, temperature, and the molar ratio of ?-CL to anhydroxylose units (AXU) on the degree of substitution (DS) of xylan-graft-poly(?-caprolactone) (xylan-g-PCL) copolymers and the degree of polymerization (DP) of the attached PCL side chains were investigated. FT-IR and NMR analyses provided the evidence of the occurrence of ROGP reaction. The thermal stability of xylan increased upon ROGP reaction due to the increased length of PCL side chains. With the increased attachment of PCL side chains, the tensile strength and Young's modulus of the films decreased, whereas the elongation at break increased. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) observations provided the evidences of the increased film properties due to the attachment of PCL side chains. PMID:25498691

Zhang, Xueqin; Chen, Mingjie; Liu, Chuanfu; Zhang, Aiping; Sun, Runcang

2015-03-01

43

Surface graft polymerization of SU-8 for bio-MEMS applications  

NASA Astrophysics Data System (ADS)

There is currently increasing interest in using SU-8 photoresist to build microstructures for micro-electro-mechanical systems (MEMS). This report describes an effective bench-top method to modify the surface properties of SU-8 photoresist. This strategy relies on the residual epoxide groups present on the surface of SU-8 following fabrication. These epoxide groups are converted into hydroxyl groups by oxidation with a high concentration of cerium(IV) ammonium nitrate (CAN) and nitric acid. Subsequently the surface hydroxyl groups are used as initiation sites for graft polymerization catalyzed by CAN in the presence of acid. A number of water-soluble polymers including poly(acrylic acid), poly(acrylamide), poly(ethylene glycol) were successfully grafted onto SU-8. The presence of surface-linked polymers was confirmed by contact angle measurements, attenuated total reflection-Fourier transform infrared spectroscopy and toluidine blue adsorption. This method was particularly useful for tailoring the surface properties of complex or enclosed microstructures, for example, microfluidic channels. In addition the grafted polymers could serve as sites for high density protein immobilization or cell attachment on Bio-MEMS.

Wang, Yuli; Pai, Jeng-Hao; Lai, Hsuan-Hong; Sims, Christopher E.; Bachman, Mark; Li, G. P.; Allbritton, Nancy L.

2007-07-01

44

A mild strategy to encapsulate enzyme into hydrogel layer grafted on polymeric substrate.  

PubMed

Although the hydrogel network has been widely investigated as a carrier for enzyme immobilization, to in situ encapsulate enzymes into a hydrogel network in an efficient, practical, and active way is still one of the great challenges in the field of biochemical engineering. Here, we report a new protocol to address this issue by encapsulating enzyme into poly(ethylene glycol) (PEG) hydrogel network grafted on polymeric substrates. In our strategy, isopropyl thioxanthone semipinacol (ITXSP) dormant groups were first planted onto the surface of a plastic matrix with low density polyethylene (LDPE) film as a model by a UV-induced abstracting hydrogen-coupling reaction. As a proof of concept, lipase, which could catalyze esterification of glucose with palmitic acid, then was in situ net-immobilized into a PEG-based hydrogel network layer through a visible light-induced surface controlled/living graft cross-linking polymerization. This strategy demonstrates the following novel significant merits: (1) in comparison with the UV irradiation or high temperature, the visible light and room temperature used provide a friendly condition to maintain activity of enzyme during immobilization; (2) the uniqueness of controlled/living cross-linking polymerization not only makes it easy to form a uniform PEG hydrogel network, which is a benefit to avoid the leakage of net-immobilizing enzyme, but also to tune the net-thickness or capacity to accommodate enzyme; and (3) as compared to systems of nanoparticles and porous matrixes, the flexible/robust end-products of the surface net-immobilizing enzyme with polymer film are more suitable to be applied in a bioreactor due to their features of easier separation and reuse. We confirmed that this catalytic film could retain almost all of its initial activity after seven batches of 24 h esterifications. The proposed strategy provides an extremely simple, effective, and flexible method for enzyme immobilization. PMID:25489918

Zhu, Xing; Ma, Yuhong; Zhao, Changwen; Lin, Zhifeng; Zhang, Lihua; Chen, Ruichao; Yang, Wantai

2014-12-23

45

Poly(N-isopropylacrylamide) brushes grafted from cellulose nanocrystals via surface-initiated single-electron transfer living radical polymerization.  

PubMed

Cellulose nanocrystals (CNCs) or nanowhiskers produced from sulfuric acid hydrolysis of ramie fibers were used as substrates for surface chemical functionalization with thermoresponsive macromolecules. The CNCs were grafted with poly(N-isopropylacrylamide) brushes via surface-initiated single-electron transfer living radical polymerization (SI-SET-LRP) under various conditions at room temperature. The grafting process was confirmed via Fourier transform IR spectroscopy and X-ray photoelectron spectroscopy and the different molecular masses of the grafts were quantified and found to depend on the initiator and monomer concentrations used. No observable damage occurred to the CNCs after grafting, as determined by X-ray diffraction. Size exclusion chromatography analyses of polymer chains cleaved from the cellulose nanocrystals indicated that a higher degree of polymerization was achieved by increasing initiator or monomer loading, most likely caused by local heterogeneities yielding higher rates of polymerization. It is expected that suspension stability, interfacial interactions, friction, and other properties of grafted CNCs can be controlled by changes in temperature and provide a unique platform for further development of stimuli-responsive nanomaterials. PMID:20843063

Zoppe, Justin O; Habibi, Youssef; Rojas, Orlando J; Venditti, Richard A; Johansson, Leena-Sisko; Efimenko, Kirill; Osterberg, Monika; Laine, Janne

2010-10-11

46

Design of pervaporation membrane for organic-liquid separation based on solubility control by plasma-graft filling polymerization technique  

SciTech Connect

Pervaporation performance through the membranes showed the same tendency as solubility results. The authors have prepared the filling-polymerized membrane for pervaporation of organic-liquid mixtures by the plasma-graft polymerization technique. The membrane is composed of two different polymers: a porous substrate which can suppress membrane swelling and a grafted polymer which forms in the pores of the substrate and exhibits selectivity due to its solubility. The objectives of the present study are to design a suitable membrane for an organic-mixture system by the control of the filling-polymer solubility. Specifically, a porous high-density polyethylene membrane and poly(methylacrylate/acrylamide) copolymer were employed as the porous substrate and grafted polymer, respectively, and grafted copolymer solubility was predicted by Hansen solubility parameters (HSP). The grafted polymer composition and its solubility behavior could be controlled by varying the monomer composition, and the solubility change was in accordance with the prediction by HSP. Pervaporation performance through the membranes showed the same tendency as solubility results. The authors concluded that an optimum pervaporation membrane can be designed on the basis of solubility control through use of these techniques for polymerization and prediction.

Yamaguchi, Takeo; Nakao, Shinichi; Kimura, Shoji (Univ. of Tokyo (Japan))

1993-05-01

47

Charge tunable zwitterionic polyampholyte layers formed in cyclic olefin copolymer microchannels through photochemical graft polymerization.  

PubMed

Zwitterionic layers immobilized on various surfaces exhibit ideal biocompatibility and antifouling capability, but direct immobilization of zwitterionic molecules provides limited choice of surface charges. In this paper, the formation of charge tunable zwitterionic polyampholyte layers onto the surface of microfluidic channels of cyclic olefin copolymer by photochemical graft polymerization of mixed acrylic monomers, [2-(acryloyloxy) ethyl] trimethyl ammonium chloride and 2-acrylamido-2-methyl-1-propanesulfonic, under UV illumination was reported. With this method, surface charge of the resulting modification layers could be tailored through the initial monomer ratio and reaction conditions. The incorporation of both monomers into the grafted layers was confirmed by X-ray photoelectron spectroscopy (XPS) and attenuated total reflection Fourier transform infrared (ATR-FTIR). The results indicate that the modified layers are hydrophilic with contact angles of 33.0-44.3°, and the isoelectric points of the modified layers can be tuned from <3 to >9 simply by adjusting the monomer ratios. Elimination of the nonspecific adsorption of proteins on the zwitterionic layers thus formed was proved by fluorescent microscopy and streaming potential measurement. The uniformity of the modified layers was verified through a comparison of electrophoresis inside the modified and native microchannels. A whole blood coagulation time measurement was performed to show its applicability. PMID:23331535

Peng, Xianglu; Zhao, Lei; Du, Gangfeng; Wei, Xuan; Guo, Jinxiu; Wang, Xiayan; Guo, Guangsheng; Pu, Qiaosheng

2013-02-01

48

Controlling the cell adhesion property of silk films by graft polymerization.  

PubMed

We report here a graft polymerization method to improve the cell adhesion property of Bombyx mori silk fibroin films. B. mori silk has evolved as a promising material for tissue engineering because of its biocompatibility and biodegradability. However, silk's hydrophobic character makes cell adhesion and proliferation difficult. Also, the lack of sufficient reactive amino acid residues makes biofunctionalization via chemical modification challenging. Our study describes a simple method that provides increased chemical handles for tuning of the surface chemistry of regenerated silk films (SFs), thus allowing manipulation of their bioactivity. By grafting pAAc and pHEMA via plasma etching, we have increased carboxylic acid and hydroxyl groups on silk, respectively. These modifications allowed us to tune the hydrophilicity of SFs and provide functional groups for bioconjugation. Our strategy also allowed us to develop silk-based surface coatings, where spatial control over cell adhesion can be achieved. This control over cell adhesion in a particular region of the SFs is difficult to obtain via existing methods of modifying the silk fibroin instead of the SF surface. Thus, our strategy will be a valuable addition to the toolkit of biofunctionalization for enhancing SFs' tissue engineering applications. PMID:24650047

Dhyani, Vartika; Singh, Neetu

2014-04-01

49

EUV lithographic radiation grafting of thermo-responsive hydrogel nanostructures  

NASA Astrophysics Data System (ADS)

Nanostructures of the thermoresponsive poly( N-isopropyl acrylamide) (PNIPAAm) and of PNIPAAm-block-poly(acrylic acid) copolymers were produced on poly(tetrafluoroethylene-co-ethyelene) (ETFE) films using extreme ultraviolet (EUV) lithographic exposure with subsequent graft-polymerization. The phase transition of PNIPAAm nanostructures at the low critical solution temperature (LCST) at 32 °C was imaged by atomic force microscopy (AFM) phase contrast measurements in pure water. Results show a higher phase contrast for samples measured below the LCST temperature than for samples above the LCST, proving that the soft PNIPAAm hydrogel transforms into a much more compact conformation above the LCST. EUV lithographic exposures were combined with the reversible addition-fragment chain transfer (RAFT)-mediated polymerization using cyanoisopropyl dithiobenzoate (CPDB) as chain transfer agent to synthesize PNIPAAm block-copolymer nanostructures.

Farquet, Patrick; Padeste, Celestino; Solak, Harun H.; Gürsel, Selmiye Alkan; Scherer, Günther G.; Wokaun, Alexander

2007-12-01

50

Functionalization of cotton fabrics by radiation induced grafting of quaternary salt to impart antibacterial property  

Microsoft Academic Search

High energy gamma radiation has been used to covalently link polymer chains of a quaternary ammonium salt containing monomer, viz. [2-(Acryloyloxyethyl)]trimethylammonium chloride (AETC) to cotton fabric by mutual radiation grafting using 2-hydroxyethyl methacrylate (2-HEMA) monomer as the grafting facilitator. Grafting yield was found to increase with the radiation dose and monomer concentration. The grafted samples have been characterized for water

N. K. Goel; Virendra Kumar; M. S. Rao; Y. K. Bhardwaj; S. Sabharwal

2011-01-01

51

Immobilized enzymes in blood plasma exchangers via radiation grafting  

NASA Astrophysics Data System (ADS)

The enzyme asparaginase was immobilized onto a porous hollow polypropylene (PP) fiber blood plasma exchange device for the treatment of acute lymphocytic leukemia. The devices were first radiation grafted with polymethacrylic acid (poly(MAAc)). This introduces carboxyl groups onto the surface of the fibers. Several variables were studied in the grafting reaction including the effects of solvent type and monomer concentration. The carboxyl groups were activated with N-hydroxy succinimide (NHS) using carbodiimide chemistry. Asparaginase was then covalently immobilized on the activated surfaces. Quantitative relationships were found relating the percent graft to the amount of immobilized enzyme which was active. The enzyme reactor was tested both in vitro and in vivo using a sheep as an animal model.

Gombotz, Wayne; Hoffman, Allan; Schmer, Gottfried; Uenoyama, Satoshi

52

Radiation-induced grafting of acrylamide onto guar gum in aqueous medium: Synthesis and characterization of grafted polymer guar-g-acrylamide  

NASA Astrophysics Data System (ADS)

Mutual radiation grafting technique has been applied to carry out grafting of acrylamide (AAm) onto guar gum (GG) using high-energy Co 60? radiation to enhance its flocculating properties for industrial effluents. The grafted product was characterized using analytical probes like elemental analysis, thermal analysis, Fourier transformed infrared (FTIR), X-ray diffraction (XRD) and scanning electron microscope (SEM). The grafting extent was observed to decrease with the dose rate and increase with the concentration of AAm. Thermo gravimetric analysis (TGA) of grafted and ungrafted samples indicated better stability of grafted product. ? and microwave radiation effect on grafted and virgin GG has also been reported.

Biswal, Jayashree; Kumar, Virendra; Bhardwaj, Y. K.; Goel, N. K.; Dubey, K. A.; Chaudhari, C. V.; Sabharwal, S.

2007-10-01

53

Modification on liquid retention property of cassava starch by radiation grafting with acrylonitrile. I. Effect of ?-irradiation on grafting parameters  

NASA Astrophysics Data System (ADS)

Radiation modification on liquid retention properties of native cassava starch, gelatinized at 85°C, by graft copolymerization with acrylonitrile was carried out by mutual irradiation to gamma-rays. A thin aluminum foil was used to cover the inner wall of the reaction vessel, so that the homopolymer concentration was reduced to be less than 1.0% with a distilled water retention value of 665 g/g of the dry weight of the saponified grafted product. Confirmation of graft copolymerization and saponification reactions was made by the infrared spectrophotometric technique. The combined effect of radiation parameters in terms of an irradiation time and a dose rate to the total dose on the extent of the grafting reaction expressed in terms of grafting parameters which directly influenced liquid retention values was evaluated in conjunction with statistical analysis.

Kiatkamjornwong, S.; Chvajarernpun, J.; Nakason, C.

1993-07-01

54

Space radiation resistant transparent polymeric materials  

NASA Technical Reports Server (NTRS)

A literature search in the field of ultraviolet and charged particle irradiation of polymers was utilized in an experimental program aimed at the development of radiation stable materials for space applications. The rationale utilized for material selection and the synthesis, characterization and testing performed on several selected materials is described. Among the materials tested for ultraviolet stability in vacuum were: polyethyleneoxide, polyvinylnaphthalene, and the amino resin synthesized by the condensation of o-hydroxybenzoguanamine with formaldehyde. Particularly interesting was the radiation behavior of poly(ethyleneoxide), irradiation did not cause degradation of optical properties but rather an improvement in transparency as indicated by a decrease in solar absorptance with increasing exposure time.

Giori, C.; Yamauchi, T.

1977-01-01

55

Development of hydrogels by radiation induced polymerization for use in slow drug delivery  

NASA Astrophysics Data System (ADS)

In the present work, in order to improve the drug release profile of indinavir sulfate, a potent inhibitor of HIV protease, controlled drug delivery systems in the form of hydrogels have been designed by a radiation graft polymerization method. These hydrogels have been prepared by using dietary fiber psyllium and binary monomers mixture of acrylamide (AAm) and 2-acrylamido-2-methylpropanesulfonic acid (AMPSA). These polymers have been characterized with cryo-SEMs, FTIR, XRD and swelling studies. The swelling of hydrogels has been determined in solution of different pH, temperature and [NaCl]. in vitro release studies of model drug indinavir sulfate in different pH have been carried out to determine the drug release mechanism. The release of dug occurred through non-Fickian mechanism.

Singh, Baljit; Bala, R.

2014-10-01

56

Influence of the microenvironment on the activity of enzymes immobilized on Teflon membranes grafted by ?-radiation  

Microsoft Academic Search

The effect of the microenvironment and immobilization method on the activity of immobilized ?-galactosidase was investigated. Immobilization was done on Teflon membranes grafted with different acrylic monomers by ?-radiation and activated by two different coupling agents through the functional groups of the grafted monomers. 2-Hydroxyethyl methacrylate (HEMA) and methacrylic acid (MAA) were grafted on the membrane, and 1,6-hexamethylenediamine (HMDA) was

M. S. Mohy Eldin; M. Portaccio; N. Diano; S. Rossi; U. Bencivenga; A. D'Uva; P. Canciglia; F. S. Gaeta; D. G. Mita

1999-01-01

57

Study on chemical, UV and gamma radiation-induced grafting of 2-hydroxyethyl methacrylate onto chitosan  

NASA Astrophysics Data System (ADS)

In the present study, 2-hydroxyethyl methacrylate has been grafted onto chitosan by using either chemical initiation, or photo-induction or gamma radiation-induced polymerisation, all under heterogeneous conditions. The evidence of grafting was provided by Fourier transform infrared spectroscopy and thermal analysis. The results concerning the effect of initiator concentration, initial monomer concentration and dose rate influencing on the yield of grafting reactions are presented. These suggest that gamma irradiation is the method that leads to higher yields of grafting.

Casimiro, M. H.; Botelho, M. L.; Leal, J. P.; Gil, M. H.

2005-04-01

58

Radiation synthesis of chitosan beads grafted with acrylic acid for metal ions sorption  

Microsoft Academic Search

Radiation-induced grafting of acrylic acid onto chitosan beads was performed in solution at a dose rate of 20.6Gy\\/min of cobalt-60 gamma rays. The effect of absorbed dose on grafting yield was investigated. The characterization of the grafted material was performed by FTIR spectroscopy and the swelling measurements at different pHs. The grafting yield increased with the increase in dose, it

S. Benamer; M. Mahlous; D. Tahtat; A. Nacer-Khodja; M. Arabi; H. Lounici; N. Mameri

2011-01-01

59

Self-assembly and chiroptical property of poly(N-acryloyl-l-amino acid) grafted celluloses synthesized by RAFT polymerization.  

PubMed

Three amphiphilic poly(N-acryloyl-l-amino acid) grafted celluloses were prepared by RAFT polymerization of N-acryloyl-l-amino acid, where amino acid is alanine, proline or glutamic acid, onto cellulose backbones. The chemical structure and solution properties of the brush copolymers were characterized with FTIR, NMR and wide angle X-ray diffraction (WAXD). The thermal stability of the brush copolymers was estimated by thermal gravimetric analysis (TGA). Circular dichroism (CD) and specific rotation measurements confirmed that these grafted celluloses had characteristic chiroptical properties. The amphiphilic brush copolymers self-assembled into micelles in the aqueous solution as confirmed by transmission electron microscopy (TEM) and dynamic light scattering (DLS) analyses. The micellar aggregates showed a tunable pH-responsive property and disaggregated to form unimolecular micelles at higher pH in diluted solutions. The brush copolymers have potential applications in controlled drug release and high-performance liquid chromatography, and so forth. PMID:25498640

Liu, Yadong; Jin, Xiaosa; Zhang, Xiaosa; Han, Miaomiao; Ji, Shengxiang

2015-03-01

60

Enhancement of the grafting performance and of the water absorption of cassava starch graft copolymer by gamma radiation  

NASA Astrophysics Data System (ADS)

Enhancement of the gamma radiation grafting of acrylonitrile onto gelatinized cassava starch was investigated. Infrared spectrometry was used to follow the chemical changes in the grafting reaction and from saponification. The saponified starch- g-PAN (HSPAN) was then characterized in terms of grafting parameters to provide a guide for the optimum total dose (kGy) and the appropriate ratio of starch/acrylonitrile for a fixed dose rate of 2.5 × 10 -1 kGy/min. Other dose rates were also carried out to obtain the appropriate result of grafting copolymerization and of water absorption. A thin aluminium foil, covering the inner wall of the reaction vessel, was found to be far more effective than any other metal films in the enhancement of the grafting reaction and the water absorption as well. Nitric acid in the medium increases the grafting yield and the water absorption. Methyl ether hydroquinone inhibitor was evaluated for its ability to increase homopolymerization and decrease graft reaction. When styrene was used as a comonomer, it hampered the grafting of acrylonitrile onto starch backbone. The water absorption capacity was improved by freeze-drying the HSPAN. The treatment of the HSPAN with aluminium trichloride hexahydrate was found to enhance the degree of wicking, but to decrease the water absorbency.

Kiatkamjornwong, Suda; Meechai, Nispa

1997-06-01

61

Radiation-grafted polymers for biomaterial applications. I. 2-hydroxyethyl methacrylate: ethyl methacrylate grafting onto low density polyethylene films  

SciTech Connect

Studies were conducted on the radiation grafting of 2-hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA) by the mutual irradation technique onto low density polyethylene. Four different solution concentrations were used, and radiation doses ranged from 0.03 to 0.50 Mrad. Four copolymer compositions having different HEMA:EMA ratios were also studied using two total monomer concentrations. The kinetics of the grafting process demonstrated by the two monomers were basically different. While EMA showed a typical diffusion-controlled kinetic pattern, HEMA exhibited a more complex behavior, the main features of which were an induction period, a slight autoacceleration and a significant drop in graft level after a maximum is reached. The difference in behavior was interpreted in terms of partitioning of monomers into the polyethlene substrate. The surface topography of the grafted films was studied by means of scanning electron microscopy. A mechanism based on osmotic cell formation was suggested for the HEMA graft system. The copolymer systems investigated showed that the graft reaction is faster in the initial stages for higher percentages of EMA in the monomer mixtures; as grafting proceeds the trend is reversed. 24 references, 16 figures, 2 tables.

Cohn, D.; Hoffman, A.S.; Ratner, B.D.

1984-08-01

62

Preparation of an ion-exchange chromatographic support by a "grafting from" strategy based on atom transfer radical polymerization.  

PubMed

A new "grafting from" strategy based on surface-initiated atom transfer radical polymerization (ATRP) was first used for the preparation of a polymer-based ion-exchange support for HPLC. The most important property of the proposed method is to be applicable for the synthesis of any type of ion exchanger in both the strong and the weak forms. Monodisperse, porous poly(glycidyl methacrylate-co-ethylene dimethacrylate), poly(GMA-co-EDM) particles 5.8 mum in size were synthesized by "modified seeded polymerization". Poly(dihydroxypropyl methacrylate-co-ethylene dimethacrylate), poly(DHPM-co-EDM) particles were then obtained by the acidic hydrolysis of poly(GMA-co-EDM) particles. The ATRP initiator, 3-(2-bromoisobutyramido)propyl(triethoxy)silane was covalently attached onto poly(DHPM-co-EDM) particles via the reaction between triethoxysilane and diol groups. In the next stage, the selected monomer carrying strong cation exchanger groups, 3-sulfopropyl methacrylate (SPM), was polymerized on the initiator-immobilized particles via surface-initiated ATRP. The degree of polymerization of SPM (i.e., length of polyionic ligand) on the particles was precisely controlled by adjusting ATRP conditions. Poly(SPM)-grafted poly(DHPM-co-EDM) particles obtained with different ATRP formulations were tried as chromatographic packing in the separation of proteins by ion-exchange chromatography. The proteins were successfully separated with higher column yields with respect to the previously proposed materials. The plate heights between 100 and 150 mum were achieved with the column packed with the particles carrying the shortest poly(SPM) chains. The plate height showed no significant increase with increasing flow rate in the range of 0.5-16 cm/min. PMID:16906734

Unsal, Ender; Elmas, Begum; Caglayan, Berna; Tuncel, Mürvet; Patir, Süleyman; Tuncel, Ali

2006-08-15

63

Functionalization of cotton fabrics by radiation induced grafting of quaternary salt to impart antibacterial property  

NASA Astrophysics Data System (ADS)

High energy gamma radiation has been used to covalently link polymer chains of a quaternary ammonium salt containing monomer, viz. [2-(Acryloyloxyethyl)]trimethylammonium chloride (AETC) to cotton fabric by mutual radiation grafting using 2-hydroxyethyl methacrylate (2-HEMA) monomer as the grafting facilitator. Grafting yield was found to increase with the radiation dose and monomer concentration. The grafted samples have been characterized for water uptake, surface morphology and thermal stability and for their antibacterial efficacy against various bacteria and were found to possess significant antibacterial activity particularly against gram-positive bacteria.

Goel, N. K.; Kumar, Virendra; Rao, M. S.; Bhardwaj, Y. K.; Sabharwal, S.

2011-11-01

64

Thermoluminescence characterization of functionalized grafted polymers and its application for radiation dosimetry at low doses  

NASA Astrophysics Data System (ADS)

Functionalized polymers were prepared by radiation-induced graft copolymerization of binary monomer system acrylic acid/acrylamide (AAc/AAm) onto low-density polyethylene (LDPE) and polypropylene (PP) films using direct radiation-grafting technique. Sulfonation was carried out for the prepared grafted copolymers using concentrated sulfuric acid (97%) at 60 degrees C for 15 min. The grafted and sulfonated grafted films found to have good properties such as thermal stability and hydrophilic properties. The sulfonated grafted films found to have a better hydrophilic character than the grafted ones due to ionic character resulted by this conversion. The thermoluminescence (TL) characteristics of a set of grafted and sulfonated films have been studied with regard to their use as off-line dosimeters in radiotherapy. The structural characterization has been performed by means of infrared spectroscopy. Their TL responses have been tested with radiotherapy beams of Co-60 photons in the dose range 0.1-7 Gy. The dosimetric characterization has yielded a very good reproducibility and is independent of the radiation energy. The TL signal is not influenced by the dose rate and exhibits a very low thermal fading. Moreover, the sensitivity of the samples compares favorably with that of the standard TLD100 dosimeters. Finally, at the same dose, the TL response for LDPE-g-P (AAm/AAc) films is higher than the PP-g-P(AAm/AAc), and the sulfonated grafted films are more sensitive to radiation than the grafted ones.

Diab, H. M.; Ghaffar, A. M.; El-Arnaouty, M. B.

2005-09-01

65

Radiation graft modification of ethylene-propylene rubber—II. Effect of additives  

NASA Astrophysics Data System (ADS)

The effect of multifunctional acrylic additives including TMPTA, PEGDA and PGTA on the radiation grafting of hydrophilic vinyl monomers onto ethylene—propylene elastomer (EPM rubbers) was studied. This work centres upon gamma irradiation-induced grafting of acrylamide (AAm), N-vinyl-2-pyrrolidone (NVP), 2-hydroxyethyl methacrylate (HEMA) and acrylonitrile (AN) onto EPM rubber by the simultaneous method. Water proved to be an effective solvent but methanol lowered grafting. Sulphuric acid was detrimental to both homopolymerisation and grafting, a result consistent with the theory proposed for the role of this additive in polymer grafting systems.

Haddadi-Asl, V.; Burford, R. P.; Garnett, J. L.

1995-02-01

66

Thermo-responsive wound dressings by grafting chitosan and poly(N-isopropylacrylamide) to plasma-induced graft polymerization modified non-woven fabrics  

NASA Astrophysics Data System (ADS)

To obtain a chitosan wound dressings with temperature-responsive characteristics, polypropylene (PP) non-woven fabric (NWF) was modified by direct current pulsed oxygen plasma-induced grafting polymerization of acrylic acid (AAc) to improve hydrophilicity and to introduce carboxylic acid groups. Conjugation of chitosan and poly(N-isopropylacrylamide) (PNIPAAm) followed by using water-soluble carbodiimide as a coupling agent to form a novel bigraft PP-g-chitosan-g-PNIPAAm wound dressing. The amount of chitosan and PNIPAAm grafted to PP-g-chitosan-g-PNIPAAm were 83.0 ± 4.6 ?g/cm2 and 189.5 ± 8.2 ?g/cm2, respectively. The surface chemical composition and microstructure of the NWF were studied by electron spectroscopy for chemical analysis (ESCA) and scanning electron microscopy (SEM). The linkages between AAc, chitosan, and PNIPAAm were confirmed with the formation of amide bonds. Physical properties of the NWF were characterized and potentials of these NWFs as wound dressings were evaluated using SD rat as the animal model. NWFs contained PNIPAAm were better than those contained only chitosan in wound healing rates and the wound areas covered by PP-g-chitosan-g-PNIPAAm wound dressings healed completely in 17 days.

Chen, Jyh-Ping; Kuo, Chang-Yi; Lee, Wen-Li

2012-12-01

67

Study on radiation-induced grafting of styrene onto chitin and chitosan  

NASA Astrophysics Data System (ADS)

Radiation-induced grafting of styrene onto chitin and chitosan powder was performed at room temperature. The effect of various conditions such as absorbed dose, solvent and oxygen on grafting was investigated. The grafting yield increased with the increase in absorbed dose. At the same dose, the grafting yield of styrene on chitosan was higher than that on chitin. The grafting reaction was promoted in the presence of methanol, and oxygen delayed the grafting reaction but did not inhibit it completely. In order to study the mechanism of grafting reaction and analyze the grafted samples, the grafted products were extracted first by benzene, then they were hydrolyzed in the presence of acid and separated by thin layer chromatography (TLC). Three different kinds of polystyrene (PS), i.e. PS grafted onto chitin, PS embedded in chitin and PS in grafting solution were gained. The variation of their molecular weight (MW) and width index of molecular weight distribution ( Mw/ Mn) determined by gel permeation chromatography (GPC) at different grafting conditions is discussed.

Pengfei, Liu; Maolin, Zhai; Jilan, Wu

2001-05-01

68

Radiation-grafting of acrylamide onto silicone rubber films for diclofenac delivery  

NASA Astrophysics Data System (ADS)

This work focuses on the pre-irradiation grafting of acrylamide (AAm) onto silicone rubber films (SR) and evaluates the effect of gamma-ray radiation conditions on the grafting yield, which in turn may influence the performance of the grafted materials as components of drug-eluting devices. Pristine and modified SR were characterized using FTIR-ATR, DSC, TGA, swelling, and water contact angle analysis in order to elucidate the effects of AAm grafting onto SR. Grafted films with content in AAm ranging from 0.81% to 22.20% showed excellent cytocompatibility against fibroblasts, and capability to uptake the anti-inflammatory drug diclofenac. Amount of drug loaded directly correlated with the grafting degree of the films. Drug release studies were performed at pH 7.4 and 37 °C (physiological conditions). Most grafted films released the drug in a sustained way for at least three hours.

Magaña, Hector; Palomino, Kenia; Cornejo-Bravo, Jose M.; Alvarez-Lorenzo, Carmen; Concheiro, Angel; Bucio, Emilio

2015-02-01

69

Mechanism of radiation polymerization of vinyl monomers in the presence of mineral additives  

Microsoft Academic Search

To solve the problem of the mechanism of radiation polymerization of vinyl monomers this research investigated the effect of solvent additives of various electronic nature on radiation copolymerization of styrene and methyl methacrylate at room temperature in the presence of KSK silica gel and magnesium oxide. ?9 It is known that electron-donatin g solvents increase the rate of anionic polymerization

T. P. Kornienko; T. G. Zelenchukova

1973-01-01

70

Radiation-induced polymerization for the immobilization of penicillin acylase  

SciTech Connect

The immobilization of Escherichia coli penicillin acylase was investigated by radiation-induced polymerization of 2-hydroxyethyl methacrylate at low temperature. A leak-proof composite that does not swell in water was obtained by adding the cross-linking agent trimethylolpropane trimethacrylate to the monomer-aqueous enzyme mixture. Penicillin acylase, which was immobilized with greater than 70% yield, possessed a higher Km value toward the substrate 6-nitro-3-phenylacetamidobenzoic acid than the free enzyme form (Km = 1.7 X 10(-5) and 1 X 10(-5) M, respectively). The structural stability of immobilized penicillin acylase, as assessed by heat, guanidinium chloride, and pH denaturation profiles, was very similar to that of the free-enzyme form, thus suggesting that penicillin acylase was entrapped in its native state into aqueous free spaces of the polymer matrix.

Boccu, E.; Carenza, M.; Lora, S.; Palma, G.; Veronese, F.M.

1987-06-01

71

Stearyl methacrylate-grafted-chitosan nanoparticle as a nanofiller for PLA: Radiation-induced grafting and characterization  

NASA Astrophysics Data System (ADS)

This paper reports a one-pot synthesis using radiation-induced grafting technique to modify biopolymer-based chitosan nanoparticles as a nanofiller for blending with poly(lactic acid) (PLA). Hydrophobic stearyl methacrylate (SMA) was grafted onto non-irradiated chitosan (CS0) and pre-irradiated chitosan with a ?-ray dose of 40 kGy (CS40) to obtain stearyl methacrylate-grafted-chitosan nanoparticles (SMA-g-CSNPs).The effects of the pre-irradiated CS, grafting doses and SMA concentrations on degree of grafting (DG) and particle formation were studied. FT-IR and XRD were used to characterize the chemical and packing structure of SMA-g-CSNPs. The particle formulation and size of SMA-g-CSNPs were observed by TEM and AFM. The spherical core-shell SMA-g-CSNPs with the size ranging from 50 to 140 nm were successfully prepared. The SMA-g-CSNPs from CS40 has higher DG and smaller particle size when compared with CS0. The SMA-g-CSNPs are able to improve the compatibility between CS and PLA.

Rattanawongwiboon, Thitirat; Haema, Kamonwon; Pasanphan, Wanvimol

2014-01-01

72

Radiation synthesis of chitosan beads grafted with acrylic acid for metal ions sorption  

NASA Astrophysics Data System (ADS)

Radiation-induced grafting of acrylic acid onto chitosan beads was performed in solution at a dose rate of 20.6 Gy/min of cobalt-60 gamma rays. The effect of absorbed dose on grafting yield was investigated. The characterization of the grafted material was performed by FTIR spectroscopy and the swelling measurements at different pHs. The grafting yield increased with the increase in dose, it reached 80% at 40 kGy irradiation dose. The removal of Pb and Cd ions from aqueous solutions was investigated with both ungrafted and grafted chitosan beads. The sorption behavior of the sorbents was examined through pH, kinetics and equilibrium measurements. Grafted chitosan beads presented higher sorption capacity for both metal ions than unmodified chitosan beads.

Benamer, S.; Mahlous, M.; Tahtat, D.; Nacer-Khodja, A.; Arabi, M.; Lounici, H.; Mameri, N.

2011-12-01

73

The radiation-induced grafting of polybutadiene onto silica  

NASA Astrophysics Data System (ADS)

The ?-ray-induced grafting of polybutadiene oligomers onto precipitated silica was investigated in the dose range up to 200 kGy by THA, FTIR, CP/MAS NMR, TEM microscopy, inverse gas chromatography (IGC), with determination of the grafting yields and the characterization of the modified silica with respect to surface energy, SiO 2-oligomer interaction and morphology. The matrix EPR spectroscopy was employed for investigating the nature of the intermediate radicals in the grafting mechanism.

Dondi, D.; Buttafava, A.; Stagnaro, P.; Turturro, A.; Priola, A.; Bracco, S.; Galinetto, P.; Faucitano, A.

2009-07-01

74

Cell engineering: nanometric grafting of poly-N-isopropylacrylamide onto polystyrene film by different doses of gamma radiation.  

PubMed

Poly-N-isopropylacrylamide was successfully grafted onto a polystyrene cell culture dish and ?-preirradiated in air. In this study, the effect of a ?-pre-irradiation dose of radiation (radiation absorbed dosages of 10, 20, 30, 40 KGy) under appropriate temperature and grafting conditions was investigated. The Fourier transform infrared spectroscopy analysis showed the existence of the graft poly-N-isopropylacrylamide (PNIPAAm) on the substrate. The optimal value of the dose for grafting was 40 KGy at 50°C. The scanning electron microscopy and atomic force microscopy (AFM) images clearly showed that increasing the absorbed dose of radiation would increase the amount of grafting. Surface topography and graft thickness in AFM images of the radiated samples showed that the PNIPAAm at the absorbed dose of radiation was properly grafted. The thickness of these grafts was about 50-100 nm. The drop water contact angles of the best grafted sample at 37°C and 10°C were 55.3 ± 1.2° and 61.2 ± 0.9° respectively, which showed the hydrophilicity and hydrophobicity of the grafted surfaces. Differential scanning calorimetry analysis also revealed the low critical solution temperature of the grafted sample to be 32°C. Thermoresponsive polymers were grafted to dishes covalently which allowed fibroblast cells to attach and proliferate at 37°C; the cells also detached spontaneously without using enzymes when the temperature dropped below 32°C. This characteristic proves that this type of grafted material has potential as a biomaterial for cell sheet engineering. PMID:20957116

Biazar, Esmaeil; Zeinali, Reza; Montazeri, Naser; Pourshamsian, Khalil; Behrouz, Mahmoud Jabarvand; Asefnejad, Azadeh; Khoshzaban, Ahad; Shahhosseini, Gholamreza; Najafabadi, Mostafa Soleimannejad; Abyani, Reza; Jamalzadeh, Hamidreza; Fouladi, Mahdi; Hagh, Sasan Rahbar F; Khamaneh, Aylar Shams; Kabiri, Soudabeh; Keshel, Saeed Heidari; Mansourkiaei, Ana

2010-01-01

75

Preparation of poly( N-isopropylacrylamide) brush grafted silica particles via surface-initiated atom transfer radical polymerization used for aqueous chromatography  

NASA Astrophysics Data System (ADS)

Thermoresponsive poly( N-isopropylacrylamide) (PNIPAAm) brushes were densely grafted onto silica surface via surface-initiated atom transfer radical polymerization (SI-ATRP). The grafting reaction started from the surfaces of 2-bromoisobutyratefunctionalized silica particles in 2-propanol aqueous solution at ambient temperature using CuCl/CuCl2/ N,N,N',N',N?-pentamethyldiethylenetriamine (PMDETA) as the catalytic system. Based on thermogravimetric analysis (TGA) results, the grafting amount and grafting density of PNIPAM chains on the surface of silica were calculated to be 1.29 mg/ m2 and 0.0215 chains/nm2, respectively. The gel permeation chromatography (GPC) result showed the relatively narrow molecular weight distribution ( M w/ M n= 1.21) of the grafted PNIPAAm. The modified silica particles were applied as high-performance liquid chromatography (HPLC) packing materials to successfully separate three aromatic compounds using water as mobile phase by changing column temperature. Temperature-dependent hydrophilic/hydrophobic property alteration of PNIPAAm brushes grafted on silica particles was determined with chromatographic interaction between stationary phase and analytes. Retention time was prolonged and resolution was improved with increasing temperature. Baseline separation with high resolution at relatively low temperatures was observed, demonstrating dense PNIPAAm brushes were grafted on silica surfaces.

Liu, Zong-Jian; Liang, Yan-Li; Geng, Fang-Fang; Lv, Fang; Dai, Rong-Ji; Zhang, Yu-Kui; Deng, Yu-Lin

2012-03-01

76

Radiation grafting of acrylic acid, methacrylic acid and polyfunctional methacrylates onto poly(vinyl chloride)  

NASA Astrophysics Data System (ADS)

Gamma and electron-beam radiation induced graftcopolymerization of acrylic acid, methacrylic acid, trimethylolpropane trimethacrylate (TMPTMA) and tetraethyleneglycol dimethacrylate (TEGDMA) onto PVC-films has been investigated. Both swelling effect and oxygen retardation effect in air radiation phase were found to be nonsignificant below the dosages of 1.2 Mrad due to the protection of free radicals by the quick formed gel's network. The graft percentage was increased with the dose-rate and the total dosage, becoming slowly levelling over the doses of 2.4 Mrad. The grafting-rate is regarded to be proportional to the n-th power of the dose- rate, where the value of n being as 1.10 ?1.38 for gamma-irradiation and 1.27 ?1.42 for electron- beam irradiation. Electron-beam irradiation, being extremely high dose-rate, stimulates the grafting-rate, especially the grafting-rate of polyfunctional TEGDMA and TMPTMA because of the quick formation of three dimensional network formed by intra- and inter-crosslinking. Although the grafting results of both gamma and electron-beam irradiation are similar, the latter irradiation favors the mass graft-processing of PVC-films. The formation of the grafted stratum on the PVC-film surfaces was found to induce the positive effects of big improvement in tensile-strength, excellent resistant toughness against the erasure of the prints on the grafted PVC-film surfaces and strong adhesive character with several adhesive chemicals.

Wang, Ung-Ping

77

The radiation grafting of vinyl monomers to cotton fabrics—II Diethylphosphatoethyl methacrylate to cotton flannelette for fire retardancy  

NASA Astrophysics Data System (ADS)

Cobalt 60 ? and electron beam radiation were used to graft diethylphosphatoethyl methacrylate, pure and in 90:10 methanol solution, to cotton cloth. This monomer, with an 11.64% phosphorus content, was especially developed by the Scott Paper Co. to develop fire retardancy. A simple pad and squeeze application followed by direct irradiation under a nitrogen atmosphere was used. Although excess monomer could be removed by washing with water, no solvent for the polymer was found so only the total "add-ons" could be measured. With 60Co irradiation, total polymerization was obtained with more than 1 Mrad but with electron beam irradiation only about 50% conversion was obtained even with 10 Mrad. No acceleration in the rates could be achieved with the viscous pure monomer as opposed to in solution. Yields adequate to impart reasonable fire retardancy could, however, be obtained with about 3 Mrad with electrons. No noticeable degradation of the polymer occured at the doses used.

Shiraishi, N.; Williams, J. L.; Stannett, V.

78

Synthesis, modification and graft polymerization of magnetic nano particles for PAH removal in contaminated water  

PubMed Central

Magnetic nanoparticles (MNPs) were modified with 3-Mercaptopropytrimethoxysiline (MPTMS) and grafted with allyl glycidyl ether for coupling with beta naphtol as a method to form a novel nano-adsorbent to remove two poly aromatic hydrocarbons (PAHs) from contaminated water. The modified MNPs were characterized by transmission electron microscopy, infrared spectroscopy and thermogravimetric analysis. Results showed that the modified MNPs enhanced the process of adsorption. Tests were done on the adsorption capacity of the two PAHs on grafted MNPs; factors applied to the tests were temperature, contact time, pH, salinity and initial concentration of PAHs. Results revealed that adsorption equilibrium was achieved in 10 min, and the maximum adsorption capacity was determined as 4.15 mg/g at pH?=?7.0 and 20°C. The equilibrium adsorption data of the two PAHs by the modified MNPs were analyzed by Langmuir, Freundlich and Temkin models. Equilibrium adsorption data was determined from the Langmuir, Freundlich and Temkin constants from tests under conditions of pH?=?7 and temperature 20°C. Analysis of the adsorption-desorption process indicated that the modified MNPs had a high level of stability and good reusability. Magnetic separation in these tests was fast and this shows that the modified MNPs have great potential to be used as a new adsorbent for the two PAHs removal from contaminated water in water treatment. PMID:25101170

2014-01-01

79

Characterization of bonding between poly(dimethylsiloxane) and cyclic olefin copolymer using corona discharge induced grafting polymerization.  

PubMed

Thermoplastics have been increasingly used for fabricating microfluidic devices because of their low cost, mechanical/biocompatible attributes, and well-established manufacturing processes. However, there is sometimes a need to integrate such a device with components made from other materials such as polydimethylsiloxane (PDMS). Bonding thermoplastics with PDMS to produce hybrid devices is not straightforward. We have reported our method to modify the surface property of a cyclic olefin copolymer (COC) substrate by using corona discharge and grafting polymerization of 3-(trimethoxysilyl)propyl methacrylate; the modified surface enabled strong bonding of COC with PDMS. In this paper, we report our studies on the surface modification mechanism using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurement. Using this bonding method, we fabricated a three-layer (COC/PDMS/COC) hybrid device consisting of elastomer-based valve arrays. The microvalve operation was confirmed through the displacement of a dye solution in a fluidic channel when the elastomer membrane was pneumatically actuated. Valve-enabled microfluidic handling was demonstrated. PMID:21962541

Liu, Ke; Gu, Pan; Hamaker, Kiri; Fan, Z Hugh

2012-01-01

80

Characterization of Bonding Between Poly(dimethylsiloxane) and Cyclic Olefin Coplymer Using Corona Discharge Induced Grafting Polymerization  

PubMed Central

Thermoplastics have been increasingly used for fabricating microfluidic devices because of their low cost, mechanical/biocompatible attributes, and well-established manufacturing processes. However, there is sometimes a need to integrate such a device with components made from other materials such as polydimethylsiloxane (PDMS). Bonding thermoplastics with PDMS to produce hybrid devices is not straightforward. We have reported our method to modify the surface property of a cyclic olefin copolymer (COC) substrate by using corona discharge and grafting polymerization of 3-(trimethoxysilyl)propyl methacrylate; the modified surface enabled strong bonding of COC with PDMS. In this paper, we report our studies on the surface modification mechanism using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurement. Using this bonding method, we fabricated a three-layer (COC/PDMS/COC) hybrid device consisting of elastomer-based valve arrays. The microvalve operation was confirmed through the displacement of a dye solution in a fluidic channel when the elastomer membrane was pneumatically actuated. Valve-enabled microfluidic handling was demonstrated. PMID:21962541

Liu, Ke; Gu, Pan; Hamaker, Kiri; Fan, Z. Hugh

2011-01-01

81

Modification of fiber properties through grafting of acrylonitrile to rayon by chemical and radiation methods  

PubMed Central

Fibrous properties of rayon has been modified through synthesis of graft copolymers of rayon with acrylonitrile (AN) by chemical method using ceric ammonium nitrate (CAN/HNO3) as a redox initiator and gamma radiation mutual method. Percentage of grafting (Pg) was determined as a function of initiator concentration, monomer concentration, irradiation dose, temperature, time of reaction and the amount of water. Maximum percentage of grafting (160.01%) using CAN/HNO3 was obtained at [CAN] = 22.80 × 10?3 mol/L, [HNO3] = 112.68 × 10?2 mol/L and [AN] = 114.49 × 10?2 mol/L in 20 mL of water at 45 °C within 120 min while in case of gamma radiation method, maximum Pg (90.24%) was obtained at an optimum concentration of AN of 76.32 × 10?2 mol/L using 10 mL of water at room temperature with total dose exposure of 3.456 kGy/h. The grafted fiber was characterized by FTIR, SEM, TGA and XRD studies. Swelling behavior of grafted rayon in different solvents such as water, methanol, ethanol, DMF and acetone was studied and compared with the unmodified rayon. Dyeing behavior of the grafted fiber was also investigated.

Kaur, Inderjeet; Sharma, Neelam; Kumari, Vandna

2013-01-01

82

Radiation grafting of styrene and maleic anhydride onto PTFE membranes and sequent sulfonation for applications of vanadium redox battery  

NASA Astrophysics Data System (ADS)

Using ?-radiation technique, poly(tetrafluoroethylene) (PTFE) membrane was grafted with styrene (St) (PTFE- graft-PS) or binary monomers of St and maleic anhydride (MAn) (PTFE- graft-PS- co-PMAn), respectively. Then grafted membranes were further sulfonated with chlorosulfonic acid into ion-exchange membranes (denoted as PTFE- graft-PSSA and PTFE- graft-PSSA- co-PMAc, respectively) for application of vanadium redox battery (VRB). Micro-FTIR analysis indicated that PTFE was successfully grafted and sulfonated at the above two different conditions. However, a higher degree of grafting (DOG) was obtained in St/MAn binary system at the same dose due to a synergistic effect. Comparing with PTFE- graft-PSSA, PTFE- graft-PSSA- co-PMAc membrane showed higher water uptake and ion-exchange capacity (IEC) and lower area resistance (AR) at the same DOG. In addition, PTFE- graft-PSSA- co-PMAc with 6% DOG also showed a higher IEC and higher conductivity compared to Nafion membrane. Radiation grafting of PTFE in St/MAn binary system and sequent sulfonation is an appropriate method for preparing ion-exchange membrane of VRB.

Qiu, Jingyi; Ni, Jiangfeng; Zhai, Maolin; Peng, Jing; Zhou, Henghui; Li, Jiuqiang; Wei, Genshuan

2007-11-01

83

Study of gamma-ray radiation-induced polymerization of butadiene in ethanol  

NASA Astrophysics Data System (ADS)

The Co 60 ?-ray radiation induced polymerization of butadiene in bulk and in ethanol at temperatures ranging from 15 to 45°C was studied. Hydrogen peroxide was used as initiator on some occasions. The mechanism of the polymerization in ethanol seems to be fitted to the no energy transfer kinetics as described by Chapiro (1962). The ratio of relative rate of free radical production of solvent/monomer ? rel is 19. When hydrogen peroxide was added, the polymerization rate increased and hydroxyl terminated polybutadiene was obtained. The microstructure of polybutadiene was studied by i.r. and NMR spectra.

Jian, Zhang; Zhiping, Zhang; Shengkang, Ying

84

Study of gamma-ray radiation induced polymerization of butadiene in ethanol  

NASA Astrophysics Data System (ADS)

The 60Co ?-ray radiation induced polymerization of butadiene in bulk and in ethanol at temperature ranging from 15 to 45°C has been studied. Hydrogen peroxide was used as initiator in some occasions. The mechanisms of polymerization in ethanol seems to fit the no-energy transfer kinetics described by Chapiro (1962) and the ratio of relative rate of free radical production of solvent/monomer ? rel is 19. When hydrogen peroxide was added to the butadiene-ethanol system the polymerization rate increased and hydroxyl terminated polybutadiene was obtained. The microstructure of polybutadiene was studied by IR and NMR spectra.

Jian, Zhang; Zhi-Ping, Zhang; Shang-Kang, Ying

85

Stability of SG1 nitroxide towards unprotected sugar and lithium salts: a preamble to cellulose modification by nitroxide-mediated graft polymerization  

PubMed Central

Summary The range of applications of cellulose, a glucose-based polysaccharide, is limited by its inherently poor mechanical properties. The grafting of synthetic polymer chains by, for example, a “grafting from” process may provide the means to broaden the range of applications. The nitroxide-mediated polymerization (NMP) method is a technique of choice to control the length, the composition and the architecture of the grafted copolymers. Nevertheless, cellulose is difficult to solubilize in organic media because of inter- and intramolecular hydrogen bonds. One possibility to circumvent this limitation is to solubilize cellulose in N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMA) with 5 to 10 wt % of lithium salts (LiCl or LiBr), and carry out grafted polymerization in this medium. The stability of nitroxides such as SG1 has not been studied under these conditions yet, even though these parameters are of crucial importance to perform the graft modification of polysaccharide by NMP. The aim of this work is to offer a model study of the stability of the SG1 nitroxide in organic media in the presence of unprotected glucose or cellobiose (used as a model of cellulose) and in the presence of lithium salts (LiBr or LiCl) in DMF or DMA. Contrary to TEMPO, SG1 proved to be stable in the presence of unprotected sugar, even with an excess of 100 molar equivalents of glucose. On the other hand, lithium salts in DMF or DMA clearly degrade SG1 nitroxide as proven by electron-spin resonance measurements. The instability of SG1 in these lithium-containing solvents may be explained by the acidification of the medium by the hydrolysis of DMA in the presence of LiCl. This, in turn, enables the disproportionation of the SG1 nitroxide into an unstable hydroxylamine and an oxoammonium ion. Once the conditions to perform an SG1-based nitroxide-mediated graft polymerization from cellobiose have been established, the next stage of this work will be the modification of cellulose and cellulose derivatives by NMP. PMID:23946859

Moreira, Guillaume; Charles, Laurence; Major, Mohamed; Vacandio, Florence; Guillaneuf, Yohann

2013-01-01

86

Hemocompatibility and anti-biofouling property improvement of poly(ethylene terephthalate) via self-polymerization of dopamine and covalent graft of zwitterionic cysteine.  

PubMed

Inspired by the composition of adhesive proteins in mussels, we used self-polymerized dopamine to form a thin and surface-adherent polydopamine layer onto poly(ethylene terephthalate) (PET) sheet, followed by covalent grafting cysteine (Cys) to improve hemocompatibility and anti-biofouling property. The obtained surfaces were characterized by water contact angle measurements (WCA), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS) analysis. The results of platelet adhesion and protein adsorption tests showed that cysteine immobilized PET was endowed with improved resistance to nonspecific protein adsorption and platelet adhesion. The results of hemolysis rate test showed cysteine grafted PET (PET-g-Cys) had low hemolytic ability. Cell assay results showed that PET-g-Cys surface could greatly inhibit HeLa cell adhesion. These works provide an ideal hemocompatible and antifouling surface for biomedical applications. PMID:23735748

Li, Pengfei; Cai, Xianmei; Wang, Ding; Chen, Shuangchun; Yuan, Jiang; Li, Li; Shen, Jian

2013-10-01

87

Specialty polymeric membranes. 8: Separation of benzene from benzene/cyclohexane mixtures with nylon 6-graft-poly(butyl methacrylate) membranes  

SciTech Connect

A novel pervaporation membrane was prepared by radical graft polymerization of butyl methacrylate onto nylon 6. The permselectivity toward benzene was increased by the introduction of poly(butyl methacrylate) onto a nylon 6 membrane. From pervaporation and sorption experiments, it was shown that the introduction of poly(butyl methacrylate) onto a nylon 6 membrane leads to the enhancement of permselectivity toward benzene. The solubility data for benzene were described by a combination of simple sorption and specific sorption, while cyclohexane solubility was described by simple sorption.

Yoshikawa, Masakazu; Tsubouchi, Keisuke; Kitao, Toshio [Kyoto Inst. of Tech., Matsugasaki, Kyoto (Japan). Dept. of Polymer Science and Engineering] [Kyoto Inst. of Tech., Matsugasaki, Kyoto (Japan). Dept. of Polymer Science and Engineering

1999-02-01

88

Modeling and optimization aspects of radiation induced grafting of 4-vinylpyridene onto partially fluorinated films  

NASA Astrophysics Data System (ADS)

Modeling and optimization aspects of radiation induced grafting (RIG) of 4-vinylpyridine (4-VP) onto partially fluorinated polymers such as poly(ethylene-co-tetrafluoroethene) (ETFE) and poly(vinylidene fluoride) (PVDF) films were comparatively investigated using response surface method (RSM). The effects of independent parameters: absorbed dose, monomer concentration, grafting time and reaction temperature on the response, grafting yield (GY) were correlated through two quadratic models. The results of this work confirm that RSM is a reliable tool not only for optimization of the reaction parameters and prediction of GY in RIG processes, but also for the reduction of the number of the experiments, monomer consumption and absorbed dose leading to an improvement of the overall reaction cost.

Nasef, Mohamed Mahmoud; Ahmad Ali, Amgad; Saidi, Hamdani; Ahmad, Arshad

2014-01-01

89

Current status of adsorbent for metal ions with radiation grafting and crosslinking techniques  

NASA Astrophysics Data System (ADS)

Removal of toxic metals from streaming water and ground water is important task to preserve environment. Radiation processing of grafting and crosslinking can synthesis adsorbent having high performances. Graft adsorbent can be synthesized by using the conventional polymer like polyethylene having variety shapes such as membrane, cloth, and fiber. Especially, the obtained fibrous adsorbent has 100 times higher rate of adsorption than that of commercialized resin. Fibrous adsorbent of iminodiacetate was applied to the removal of cadmium from the scallop waste. Furthermore, the amidoxime adsorbent is useful for recovery of rare metals such as uranium and vanadium in seawater. Novel fibrous adsorption for arsenic was synthesized by direct grafting of phosphoric monomer and following zirconium-loading. Crosslinked natural polymers like carboxymethyl chitin-chitosan in the paste-like state are applicable for the metal adsorbent. This adsorbent can be biodegraded after usage.

Seko, Noriaki; Tamada, Masao; Yoshii, Fumio

2005-07-01

90

Preparation of Modified Chitosan by Graft Polymerization and its Adsorption of Cd2+ and Co2+ from Binary Solution  

NASA Astrophysics Data System (ADS)

The grafting copolymerization of chitosan with acrylamide and acrylonitrile was studied which initiated by NaHSO3-K2S2O8. And the chitosan-acrylamide-acrylonitrile ternary graft copolymer was synthesized in N2 atmosphere. Under the optimal experimental conditions, the average graft ratio and the graft efficiency could up to 852.46% and 85.26%, respectively. The adsorption selectivity and influences to the adsorption by factors like adsorption time, adsorption temperature, initial concentration of metal ion and initial pH of the solution were studied. The results showed that: the adsorption selectivity was obtained of the ternary graft copolymer to Cd2+; under the same experimental conditions, the maximum difference of adsorption rate between Cd2+ and Co2+ by polymer would be 31.07%.

Bi, Qiang; Xue, Juanqin; Guo, Yingjuan; Mao, Weibo; Wang, Yujie

2013-07-01

91

Synthesis of polyphenylacetylene by radiation-induced polymerization in deoxycholic acid clathrate  

NASA Astrophysics Data System (ADS)

Phenylacetylene was polymerized as inclusion compound (clathrate) inside deoxycholic acid (DOCA) crystals. The polymerization was initiated by ? radiation and a total dose of 320 kGy was employed. The resulting polyphenylacetylene (PPA) was isolated by dissolution of deoxycholic acid in boiling ethanol. PPA high polymer was accompanied by a series of phenylacetylene oligomers, which were detected by liquid chromatographic analysis (HPLC). PPA was characterized by electronic absorption spectroscopy and by FT-IR spectroscopy in comparison to a reference PPA prepared by a stereospecific catalyst. The microstructure of PPA from inclusion polymerization was highly trans type, similar to that observed on PPA prepared by bulk radiolysis. No optical activity was detected by polarimetry on PPA prepared by inclusion polymerization. The host-guest complex PPA/DOCA was studied by differential thermal analysis (DTA) and by thermogravimetry (TGA). DTA provided evidences of the host-guest complex formation from the shift of the melting point of DOCA while the TGA confirmed the identity - in terms of thermal behaviour - of the PPA from inclusion polymerization with that from stereospecific polymerization.

Cataldo, Franco; Strazzulla, Giovanni; Iglesias-Groth, Susana

2009-04-01

92

Synthesis and characterization of thermo- and pH- sensitive hydrogels based on Chitosan-grafted N-isopropylacrylamide via ?-radiation  

NASA Astrophysics Data System (ADS)

Thermo- and pH-sensitive hydrogels were prepared by graft copolymerization of chitosan (CS) and N-isopropylacrylamide via ?-radiation. The effects of monomer concentration and irradiation dose on grafting percentage and grafting efficiency were studied. The graft copolymers were characterized by 13C CP/MAS NMR and thermogravimetric analysis. The pH and thermosensitivity and swelling properties of the hydrogels were investigated. The results showed that the grafting percentage and grafting efficiency increased with the increase of monomer concentration and total irradiation dose. The highest grafting percentage is 620%, the lower critical solution temperature (LCST) of this hydrogel is about 28 °C.

Cai, Hong; Zhang, Zheng Pu; Chuan Sun, Ping; Lin He, Bing; Xia Zhu, Xiao

2005-09-01

93

Influence of matrix porosity on the immobilization of penicillin acylase by radiation-induced polymerization  

NASA Astrophysics Data System (ADS)

Penicillin acylase was immobilized by low temperature radiation-induced polymerization into polymer matrices obtained from monomers of different hydrophilicities, at various ratios of monomer to enzyme solution and at different polymerization conversions. It was found that the penicillin acylase retention (60-85% of the starting enzyme) is independent of the monomer used in thepolymerization, of the polymerization conversion and of the porosity of the polymer matrix. On the other hand, the penicillin acylase retention strongly depends on the presence in the irradiation mixture of the hydrophobic crosslinking agent, trimethylolpropane trimethacrylate, even in low amounts. The data suggest that the enzyme is bound to the polymer matrix by hydrophobic interactions through crosslinking agent molecules.

Carenza, M.; Lora, S.; Palma, G.; Boccù, E.; Largajolli, R.; Veronese, F. M.

94

Radiation grafting of hydrophilic monomers on to plasticized poly(vinyl chloride) sheets  

Microsoft Academic Search

Medical-grade plasticized poly(vinyl chloride) (PVC) sheets were surface modified using gamma-radiation grafting of a combination of hydrophilic monomers based on 2-hydroxyethyl methacrylate (HEMA) and N-vinyl pyrrolidone (NVP). The modified surfaces were evaluated for their surface properties using contact angle measurements, phase-contrast photomicroscopy and scanning electron microscopy. Surface energy calculations of the modified surfaces indicated that the surfaces became highly hydrophilic

V. Kalliyana Krishnan; A. Jayakrishnan; Joseph D. Francis

1990-01-01

95

Radiation grafting of hydrophilic monomers onto plasticized poly(vinyl chloride) sheets  

Microsoft Academic Search

Medical grade poly(vinyl chloride) (PVC) sheets were surface modified by grafting a combination of 2-hydroxyethyl methacrylate (HEMA) and N-vinyl pyrrolidone (NVP) or NVP alone using gamma radiation in an effort to retard the migration of the plasticizer from the PVC matrix. Presence of cupric ions at a concentration of 0.005m was found to be optimal in not only preventing the

V. Kalliyana Krishnan; A. Jayakrishnan; J. D. Francis

1991-01-01

96

Revival of the R-group approach: a "CTA-shuttled" grafting from approach for well-defined cylindrical polymer brushes via RAFT polymerization.  

PubMed

The synthesis of well-defined cylindrical polymer brushes (CPBs) from a linear polymer backbone with a high density of RAFT functionalities ("grafting from" approach) is challenging when the chain transfer agent (CTA) is attached to the backbone via its R-group. It is proposed that the difficulties of the R-group approach in controlling the grafting polymerization are induced by the "entrapment" of active free radicals within individual growing CPBs. A facile "CTA-shuttled" R-group approach overcoming this entrapment effect is developed, and used to synthesize well-defined CPBs with polystyrene or poly(tert-butyl acrylate) branches and core-shell CPBs with polystyrene-block-poly(N-isopropylacrylamide) branches. The polydispersity index (PDI = 1.23) of the obtained CPBs with polystyrene branches is much lower than that from the conventional R-group approach (PDI = 2.18). Monte Carlo simulations confirm that the advantage of the "CTA-shuttled" R-group approach consists in the release of the active radicals from the trapping CPB systems. PMID:24115272

Zheng, Zhicheng; Ling, Jun; Müller, Axel H E

2014-01-01

97

Role of polymeric endosomolytic agents in gene transfection: a comparative study of poly(L-lysine) grafted with monomeric L-histidine analogue and poly(L-histidine).  

PubMed

Endosomal entrapment is one of the main barriers that must be overcome for efficient gene expression along with cell internalization, DNA release, and nuclear import. Introducing pH-sensitive ionizable groups into the polycationic polymers to increase gene transfer efficiency has proven to be a useful method; however, a comparative study of introducing equal numbers of ionizable groups in both polymer and monomer forms, has not been reported. In this study, we prepared two types of histidine-grafted poly(L-lysine) (PLL), a stacking form of poly(L-histidine) (PLL-g-PHis) and a mono-L-histidine (PLL-g-mHis) with the same number of imidazole groups. These two types of histidine-grafted PLL, PLL-g-PHis and PLL-g-mHis, showed profound differences in hemolytic activity, cellular uptake, internalization, and transfection efficiency. Cy3-labeled PLL-g-PHis showed strong fluorescence in the nucleus after internalization, and high hemolytic activity upon pH changes was also observed from PLL-g-PHis. The arrangement of imidazole groups from PHis also provided higher gene expression than mHis due to its ability to escape the endosome. mHis or PHis grafting reduced the cytotoxicity of PLL and changed the rate of cellular uptake by changing the quantity of free ?-amines available for gene condensation. The subcellular localization of PLL-g-PHis/pDNA measured by YOYO1-pDNA intensity was highest inside the nucleus, while the lysotracker, which stains the acidic compartments was lowest among these polymers. Thus, the polymeric histidine arrangement demonstrate the ability to escape the endosome and trigger rapid release of polyplexes into the cytosol, resulting in a greater amount of pDNA available for translocation to the nucleus and enhanced gene expression. PMID:25144273

Hwang, Hee Sook; Hu, Jun; Na, Kun; Bae, You Han

2014-10-13

98

Synthesis and characterization of thermo- and pH sensitive hydrogels based on Chitosan-grafted N-isopropylacrylamide via ?-radiation  

Microsoft Academic Search

Thermo- and pH-sensitive hydrogels were prepared by graft copolymerization of chitosan (CS) and N-isopropylacrylamide via ?-radiation. The effects of monomer concentration and irradiation dose on grafting percentage and grafting efficiency were studied. The graft copolymers were characterized by 13C CP\\/MAS NMR and thermogravimetric analysis. The pH and thermosensitivity and swelling properties of the hydrogels were investigated. The results showed that

Hong Cai; Zheng Pu Zhang; Ping Chuan Sun; Bing Lin He; Xiao Xia Zhu

2005-01-01

99

Hydrocarbon proton-conductive membranes prepared by radiation-grafting of styrenesulfonate onto aromatic polyamide films  

NASA Astrophysics Data System (ADS)

Novel method for preparing aromatic hydrocarbon proton-conductive membranes without sulfonation and membrane casting process is achieved by radiation-grafting of sodium styrenesulfonate to an aromatic polyamide, poly( m-xylylene adipamide) (Nylon-MXD6) films and subsequent ion-exchange. The styrenesulfonate was easily grafted into the Nylon-MXD6 films from an oxygen-free dimethyl sulfoxide (DMSO) solution at 60 °C. As a result, the resulted styrenesulfonic acid-grafted Nylon-MXD6 films, namely proton-conductive membrane, with high ion-exchange capacity up to 1.63 mmol/g, can be obtained. The membrane was transparent and highly hydrophilic. The proton conductivity, water uptake and methanol permeability of the proton-conductive membranes were investigated with respect to their use in fuel cells. The high proton conductivity reached 0.083 S/cm, comparable to Nafion. Furthermore, the methanol permeability was significantly lower than that of the Nafion membrane. Therefore, the Nylon-MXD6-based proton-conductive membrane is a more promising material for the direct methanol fuel cells (DMFCs).

Li, Dengrong; Chen, Jinhua; Zhai, Maolin; Asano, Masaharu; Maekawa, Yasunari; Oku, Hiroyuki; Yoshida, Masaru

2009-01-01

100

Radiation-induced cationic polymerization of limonene oxide,. cap alpha. -pinene oxide, and. beta. -pinene oxide  

SciTech Connect

After suitable drying, the subject monomers in the form of neat liquids undergo radiation-induced polymerization with no apparent side reactions and high conversions to precipitatable polymers of low molecular weight. A cationic mechanism is evidenced by the strongly retarding effect of tri-n-propylamine on the polymerization rate. At 25/sup 0/C, limonene oxide gives the highest polymerization rates, an average conversion of 36% per Mrad being obtained in comparison with values of 5.7 and 7.3% per Mrad for the ..cap alpha..-pinene and ..beta..-pinene oxides, respectively. Similarly, the average anti DP/sub n/ decreases from 11.8 for the limonene oxide polymer to 5.6 and 4.0 for the ..cap alpha..-pinene oxide and ..beta..-pinene oxide polymers, respectively. A high frequency of chain transfer to monomer is indicated in each case by the fact that the kinetic chain lengths are estimated to be on the order of a hundred times larger than the anti DP/sub n/ values. Structural characterization of the limonene oxide polymer by /sup 1/H and /sup 13/C NMR spectroscopy provides conclusive evidence that the polymerization proceeds by the opening of the epoxide ring to yield a 1,2-trans polyether. Similar NMR studies on the polymers formed from the ..cap alpha..-pinene and ..beta..-pinene oxides show that in the polymerization of these monomers, the opening of the epoxide ring is generally accompanied by the concomitant ring opening of the cyclobutane ring structure to yield a gem-dimethyl group in the main chain. The detection of isopropenyl end groups in the pinene oxide polymers is also consistent with this mode of propagation being followed by chain (proton) transfer to monomer.

Aikins, J.A.; Williams, F.

1984-01-01

101

Characterization and fuel cell testing of radiation-grafted PSI membranes  

SciTech Connect

The authors have demonstrated earlier the useful performance of PSI radiation-grafted membranes in terms of the current-voltage characteristics of 30 cm{sup 2} active area fuel cells containing these membranes and their long-term testing over 6,000 h at 60 C. They report here on testing of PSI radiation-grafted membranes in these fuel cells at 80 C and in short stacks comprised of two or four 100 cm{sup 2} active area cells. The in-situ degradation of membranes has been investigated by characterizing membranes both before testing in fuel cells and post-mortem after testing in fuel cells. Characterization was accomplished by means of ion-exchange capacity and infrared and Raman spectroscopic measurements. In addition, a rapid screening method for ex-situ testing of the oxidative stability of proton-conducting membranes was developed in this work. Comparison of the initial screening test results concerning the oxidative stability of some perfluorinated, partially-fluorinated, and non-fluorinated membranes compare well qualitatively with the relative stability of these same membranes during their long-term testing in fuel cells.

Brack, H.P.; Koebel, M.M.; Tsukada, A.; Huslage, J.; Buechi, F.; Geiger, F.; Rota, M.; Scherer, G.G.

2000-07-01

102

Ionic polymer-metal composite actuators obtained from radiation-grafted cation- and anion-exchange membranes.  

PubMed

Two series of ionic polymer-metal composites (IPMCs), one cationic and one anionic, are designed and prepared from radiation-grafted ion-exchange membranes. Through examination of the properties of the membranes synthesized from the two grafting monomers and the two base polymers, acrylic acid-grafted poly(vinylidene fluoride-co-hexafluoropropylene) and quarternized 4-vinylpyridine-grafted poly(ethylene-co-tetrafluoroethylene) with the appropriate amount of ionic groups are employed for the fabrication of cation and anion IPMCs, respectively. The bending displacement of the cation IPMC is comparable to Nafion-based IPMC under direct- and alternating-current voltage, but back-relaxation is not observed. The actuation performance of the anion IPMC is highly improved over those reported earlier in the literature for the other anion IPMCs. PMID:25420910

Park, Jong Hyuk; Han, Man Jae; Song, Dae Seock; Jho, Jae Young

2014-12-24

103

Novel ion-exchange membranes for electrodialysis prepared by radiation-induced graft polymerization  

Microsoft Academic Search

Ion-exchange membranes have been used to concentrate seawater to produce salt as well as to desalinate brackish water to render it potable. Also, the interest in applications of ion-exchange membranes as separators for electrodialytic desalination of bioproducts and separators in hydrogen-oxygen fuel cells has been growing. Novel ion-exchange membranes containing sulfonic acid (SOâH) and trimethyl ammonium [N(CHâ)â] groups were prepared

Satoshi Tsuneda; Kyoichi Saito; Hisashi Misuhara; Takanobu Sugo

1995-01-01

104

PDMS-Glass bonding using grafted polymeric adhesive - Alternative process flow for compatibility with patterned biological molecules  

PubMed Central

We report a novel modification of silicone elastomer, polydimethylsiloxane (PDMS) with a polymer graft that allows interfacial bonding between elastomer and glass substrate to be performed without exposure of said substrate to harsh treatment conditions like oxygen plasma. Organic molecules can thus be patterned within microfluidic channels and still remain functional post-bonding. In addition, after polymer grafting the PDMS can be stored in a desiccator for at least 40 days, and activated upon exposure to acidic buffer for bonding. The bonded devices remain fully bonded in excess of 80 psi driving pressure, with no signs of compromise to the bond integrity. Finally, we demonstrate the compatibility of our method with biological molecules using a proof-of-concept DNA sensing device, in which fluorescently-labelled DNA targets are successfully captured by a patterned probe in a device sealed using our method, while the pattern on a plasma-treated device was completely destroyed. Therefore, this method provides a much-needed alternative bonding process for incorporation of biological molecules in microfluidic devices. PMID:22858861

Beh, Cyrus Weijie; Zhou, Weizhuang

2013-01-01

105

Grafting of methyl methacrylate to cellulose and polypropylene with UV and ionising radiation in the presence of additives including CT complexes  

Microsoft Academic Search

Detailed studies of the grafting of polar methyl methacrylate (MMA) to two representative backbone polymers, cellulose and polypropylene (PPE) in the presence of additives, using ionising radiation and UV as initiating sources, are reported. The results are compared with analogous grafting work with non polar styrene previously studied. The additives chosen for examination were predominantly components used in radiation curing

John L. Garnett; Loo-Teck Ng; Visay Viengkhou

1999-01-01

106

Preparation of PTFE-based fuel cell membranes by combining latent track formation technology with graft polymerization  

NASA Astrophysics Data System (ADS)

Swift heavy 56 MeV 15N 3+ ions were generated with particle fluences of 0, 3×10 6, 3×10 7, 3×10 8, 3×10 9 ions/cm 2 to form a latent track zone in a 25-?m-thick film of polytetrafluoroethylene (iPTFE). Styrene (St) was then grafted onto the iPTFE films by UV-irradiation or pre-?-irradiation, and after sulfonation iPTFE-based proton-conducting membranes were obtained, here called, iPTFE-g(UV)-PStSA and iPTFE-g(?)-PStSA membranes, respectively, which had a straight cylindrical damage zone around the ion path. The degree of grafting was found to be about 7.5% with a particle fluence of 3×10 7 ions/cm 2 and with either the UV-method or the ?-method. The ion-exchange capacity, proton conductivity in the thickness direction, MeOH permeability, tensile strength and elongation at break of the obtained iPTFE-g(UV)-PStSA membrane were 0.50 mmol/g, 0.06 S/cm, 0.15×10 -6 cm 2/s, 50 MPa and 600%, in contrast to 0.06 mmol/g, 0.06 S/cm, 0.35×10 -6 cm 2/s, 19 MPa and 210% for the iPTFE-g(?)-PStSA membrane, respectively. In comparison, the Nafion 112 measured in our laboratory exhibited an ion-exchange capacity of 0.91 mmol/g, a proton conductivity of 0.06 S/cm, a MeOH permeability of 1.02×10 -6 cm 2/s, a tensile strength of 35 MPa and an elongation at break of 295%. It can be concluded from these data that the lower crossover of MeOH, the same proton conductibility, the lower ion-exchange capacity, and the superior mechanical properties of the UV-grafted proton-conducting membranes compared to the Nafion make them promising materials for widespread application in direct methanol fuel cells. On the other hand, the tests of mechanical strength showed that the PTFE base film is subject to degradation by the ion-beam irradiation as well as the ?-irradiation.

Yoshida, Masaru; Kimura, Yosuke; Chen, Jinhua; Asano, Masaharu; Maekawa, Yasunari

2009-12-01

107

Radiolytic method of preparation of semiconductor assemblies supported on polymeric membranes  

NASA Astrophysics Data System (ADS)

Radiation induced grafting of hydrophilic acrylic monomers onto polymeric films and fabric has been employed to prepare supports for catalytic assemblies, which are highly permeable to water and low molecular weight solutes. Transition-metal-oxide semiconductor clusters embedded within the grafted membranes were formed by swelling the membranes with a solution of metal alkoxides followed by gradual hydrolysis. Photolytic methods have been employed to form Pt° clusters onto the semiconductor agregates. Kinetic aspects of the radiation induced grafting of the polymeric supports and the mechanistic features of the preparation of polymer-anchored TiO 2 clusters loaded with Pt° are described. The photocatalytic effectiveness of the TiO 2-Pt assemblies embedded in recoverable polymeric grids was demonstrated in hydrogen generation from aqueous solution and in the degradation of environmental pollutants.

Haruvy, Y.; Gratzel, M.; Rajbenbach, L. A.

108

Synthesis of poly(N-isopropylacrylamide) hydrogels by radiation polymerization and cross-linking  

SciTech Connect

Poly(N-isopropylacrylamide) [poly(NIPAAm)] shows a typical thermal reversibility of phase transition in aqueous solutions. That is, it precipitates from solution above a critical temperature called the lower critical solution temperature (LCST) and dissolves below this temperature. When it is cross-linked, the obtained hydrogel collapses above LCST, while it swells and expands below LCST. This hydrogel has received much attention recently and has been used as a model system to demonstrate the validity of theories describing the coil-globule transition, swelling of networks, and folding and unfolding of biopolymers. It has also been proposed for various applications ranging from controlled drug delivery to solute separation. Poly(NIPAAm) hydrogel is usually synthesized at room temperature from an aqueous solution of the monomer by using a redox initiator composed of ammonium persulfate and N,N,N{prime},N{prime}-tetramethylethylenediamine in the presence of N,N{prime}-methylenebisacrylamide as a cross-linker. Since the LCST of poly(NIPAAm) is around 32 C, the polymerization at room temperature proceeds in a homogeneous solution. Recently, poly(NIPAAm) hydrogels were synthesized by starting the polymerization below the LCST and then elevating the temperature above it, by which method macroporous gels with fast temperature response were obtained. The idea is to apply a radiation--induced polymerization method for the synthesis of poly(NIPAAm) hydrogels. This method offers unique advantages for synthesis: it is a simple and additive-free process at all temperatures, and the degree of cross-linking can be easily controlled by irradiation conditions. Therefore, radiation methods are especially attractive for the synthesis of hydrogels with potential biomedical application where the residual chemical initiators may contaminate the product. It is possible to combine into one step the synthesis and sterilization of the product, and it is economically competitive.

Nagaoka, Noriyasu; Kubota, Hitoshi; Katakai, Ryoichi [Gunma Univ. (Japan). Dept. of Chemistry; Safranj, Agneza; Yoshida, Masaru; Omichi, Hideki [Japan Atomic Energy Research Inst., Gunma (Japan). Dept. of Material Development

1993-12-20

109

Gold-Loaded Polymeric Micelles for Computed Tomography-Guided Radiation Therapy Treatment and Radiosensitization  

PubMed Central

Gold nanoparticles (AuNPs) have generated interest as both imaging and therapeutic agents. AuNPs are attractive for imaging applications since they are nontoxic and provide nearly three times greater X-ray attenuation per unit weight than iodine. As therapeutic agents, AuNPs can sensitize tumor cells to ionizing radiation. To create a nanoplatform that could simultaneously exhibit long circulation times, achieve appreciable tumor accumulation, generate computed tomography (CT) image contrast, and serve as a radiosensitizer, gold-loaded polymeric micelles (GPMs) were prepared. Specifically, 1.9 nm AuNPs were encapsulated within the hydrophobic core of micelles formed with the amphiphilic diblock copolymer poly(ethylene glycol)-b-poly(?-capralactone). GPMs were produced with low polydispersity and mean hydrodynamic diameters ranging from 25 to 150 nm. Following intravenous injection, GPMs provided blood pool contrast for up to 24 h and improved the delineation of tumor margins via CT. Thus, GPM-enhanced CT imaging was used to guide radiation therapy delivered via a small animal radiation research platform. In combination with the radiosensitizing capabilities of gold, tumor-bearing mice exhibited a 1.7-fold improvement in the median survival time, compared with mice receiving radiation alone. It is envisioned that translation of these capabilities to human cancer patients could guide and enhance the efficacy of radiation therapy. PMID:24377302

2013-01-01

110

Radiation-induced graft copolymerization of poly(ethylene glycol) monomethacrylate onto deoxycholate-chitosan nanoparticles as a drug carrier  

NASA Astrophysics Data System (ADS)

Poly(ethylene glycol) monomethacrylate-grafted-deoxycholate chitosan nanoparticles (PEGMA-g-DCCSNPs) were successfully prepared by radiation-induced graft copolymerization. The hydrophilic poly(ethylene glycol) monomethacrylate was grafted onto deoxycholate-chitosan in an aqueous system. The radiation-absorbed dose is an important parameter on degree of grafting, shell thickness and particle size of PEGMA-g-DCCSNPs. Owing to their amphiphilic architecture, PEGMA-g-DCCSNPs self-assembled into spherical core-shell nanoparticles in aqueous media. The particle size of PEGMA-g-DCCSNPs measured by TEM varied in the range of 70-130 nm depending on the degree of grafting as well as the irradiation dose. Berberine (BBR) as a model drug was encapsulated into the PEGMA-g-DCCSNPs. Drug release study revealed that the BBR drug was slowly released from PEGMA-g-DCCSNPs at a mostly constant rate of 10-20% in PBS buffer (pH 7.4) at 37 °C over a period of 23 days.

Pasanphan, Wanvimol; Rattanawongwiboon, Thitirat; Rimdusit, Pakjira; Piroonpan, Thananchai

2014-01-01

111

Peptide immobilization onto radiation grafted PVDF-g-poly(acrylic acid) films  

NASA Astrophysics Data System (ADS)

Introducing hydrophilic functions on poly(vinylidene fluoride) (PVDF) films surface allows the covalent immobilization of peptides. Therefore radiation grafting of acrylic acid (AA) in pre-irradiated PVDF films was achieved to allow surface functionalization with linear and cyclic peptides. Peptides were bound via spacer molecules using EDC as a coupling agent. The reactions were followed by Fourier Transform Infrared (FTIR) spectroscopy in attenuated total reflection (ATR) mode. The amount of immobilized peptides was determined by UV spectroscopy. As well, an uncommon method for PVDF characterization and reactions quantification was used: high-resolution-magic angle spinning nuclear mass spectroscopy (HR-MAS NMR). Spacer saturation of the film surface corresponded to 25 mol% yield meaning that one spacer on 4 carboxylic acids was covalently bound. XPS experiments were also performed to deepen analysis of the surface composition. Peptide density is governed by steric hindrance. ELISA tests showed that the peptides' activity is maintained.

Clochard, M.-C.; Betz, N.; Goncalves, M.; Bittencourt, C.; Pireaux, J.-J.; Gionnet, K.; Déléris, G.; Moël, A. Le

2005-07-01

112

The synthesis and characterization of hydroxyapatite-?-alanine modified by grafting polymerization of ?-benzyl-L-glutamate-N-carboxyanhydride.  

PubMed

In this study, hydroxyapatite (HAP) was surface-modified by the addition of ?-alanine (?-Ala), and the ring-opening polymerization of ?-benzyl-L-glutamate-N-carboxy-anhydride (BLG-NCA) was subsequently initiated. HAP containing surface poly-?-benzyl-L-glutamates (PBLG) was successfully prepared in this way. With the increase of PBLG content in HAP-PBLG, the solubility of HAP-PBLG increased gradually and it was ultimately soluble in chloroform. HAP-PLGA with surface carboxyl groups was obtained by the catalytic hydrogenation of HAP-PBLG. In the process of HAP modification, the morphology changes from rod to sheet and from flake to needle. The effect of BLG-NCA concentration on the character of hydroxyapatite-?-alanine-poly(?-benzyl-L-glutamate) (HAP-PBLG) was investigated. The existence of amino acids on the HAP surfaces was confirmed in the resulting Fourier transform infrared (FTIR) spectra. The resulting powder X-ray diffraction patterns indicated that the crystallinity of HAP decreased when the ratio of BLG-NCA/HAP-NH2 increased to 20/1. Transmission electron microscopy (TEM) indicated that the particle size of HAP-PBLG decreased significantly and that the resulting particles appeared less agglomerated relative to that of the HAP-NH? crystals. Furthermore, ¹H-NMR spectra and FTIR spectra revealed that hydroxyapatite-?-alanine-poly (L-glutamic acid) (HAP-PLGA) was able to successfully bear carboxylic acid groups on its side chains. PMID:24232735

Shan, Yukai; Qin, Yuyue; Chuan, Yongming; Li, Hongli; Yuan, Minglong

2013-01-01

113

Radiation-induced cationic polymerization of limonene oxide,. cap alpha. -pinene oxide, and. beta. -pinene oxide  

SciTech Connect

After suitable drying, the subject monomers in the form of neat liquids undergo radiation-induced polymerization with no apparent side reactions and high conversions to precipitatable polymers of low molecular weights. A high frequency of chain (proton) transfer to monomer is indicated by the fact that the kinetic chain lengths are estimated to be several hundred times larger than the range of DP/sub n/ values (12-4). Structural characterization of the limonene oxide polymer by /sup 1/H and /sup 13/C NMR spectroscopy provides conclusive evidence that the polymerization proceeds by the opening of the epoxide ring to yield a 1,2-trans polyether. Similar NMR studies on the polymers formed from the ..cap alpha..-pinene and ..beta..-pinene oxides show that the opening of the epoxide ring for these monomers is generally accompanied by the concomitant ring opening of the cyclobutane ring structure to yield a gem-di-methyl group in the main chain.

Aikins, J.A.; Williams, F.

1985-01-01

114

Characterization of Network Structure of Polyacrylamide Based Hydrogels Prepared By Radiation Induced Polymerization  

SciTech Connect

In this study network structure of polyacrylamide based hydrogels prepared by radiation induced polymerization has been investigated. Polyacrylamide based hydrogels in the rod form were prepared by copolymerization of acrylamide(AAm) with hydroxyl ethyl methacrylate(HEMA) and methyl acrylamide(MAAm) in the presence of cross-linking agent and water by gamma rays at ambient temperature. Molecular weight between cross-links and effective cross-link density of hydrogels were calculated from swelling as well as shear modulus data obtained from compression tests. The results have shown that simple compression analyses can be used for the determination of effective cross-link density of hydrogels without any need to some polymer-solvent based parameters as in the case of swelling based determinations. Diffusion of water into hydrogels was examined by analyzing water absorption kinetics and the effect of network, structure on the diffusion type and coefficient was discussed.

Mahmudi, Naim [State University of Tetovo, Faculty of Natural Science and Mathematics, 1200 Tetovo (Macedonia, The Former Yugoslav Republic of); Sen, Murat; Gueven, Olgun [Hacettepe University, Department of Chemistry, Polymer Chemistry Division, 06532, Beytepe, Ankara (Turkey); Rendevski, Stojan [Institute of Physics, Faculty of Natural Science and Mathematics, University 'Ss Cyril and Methodius', Skopje (Macedonia, The Former Yugoslav Republic of)

2007-04-23

115

Measurements of the temperature dependence of radiation induced conductivity in polymeric dielectrics  

NASA Astrophysics Data System (ADS)

This study measures Radiation Induced Conductivity (RIC) in five insulating polymeric materials over temperatures ranging from ~110 K to ~350 K: polyimide (PI or Kapton HN(TM) and Kapton E(TM)), polytetraflouroethylene (PTFE or Teflon(TM)), ethylene-tetraflouroethylene (ETFE or Tefzel(TM)), and Low Density Polyethylene (LDPE). RIC occurs when incident ionizing radiation deposits energy and excites electrons into the conduction band of insulators. Conductivity was measured when a voltage was applied across vacuum-baked, thin film polymer samples in a parallel plate geometry. RIC was calculated as the difference in sample conductivity under no incident radiation and under an incident ~4 MeV electron beam at low incident dose rates of 0.01 rad/sec to 10 rad/sec. The steady-state RIC was found to agree well with the standard power law relation, sigmaRIC(D?) = kRIC(T) D?Delta(T) between conductivity, sigmaRIC and adsorbed dose rate, D?. Both the proportionality constant, kRIC, and the power, Delta, were found to be temperature-dependent above ~250 K, with behavior consistent with photoconductivity models developed for localized trap states in disordered semiconductors. Below ~250 K, kRIC and Delta exhibited little change in any of the materials.

Gillespie, Jodie

116

Application of radiation grafted media for lectin affinity separation and urease immobilization: A novel approach to tumor therapy and renal disease diagnosis  

NASA Astrophysics Data System (ADS)

Carriers modified by synergistic radiation grafting are used as affinity media for the separation of a lectin from a mistletoe extract. The grafted supports show distinctly superior properties when compared to conventional affinity media. The application of these carriers as urease immobilization support incorporated in a conductimetric bioreactor for urea analysis as potential diagnostic device in renal diseases is also described.

Müller-Schulte, D.; Daschek, W.

1995-09-01

117

Highly permselective membrane surface modification by cold plasma-induced grafting polymerization of molecularly imprinted polymer for recognition of pyrethroid insecticides in fish.  

PubMed

Specific molecularly imprinted membranes (MIMs) for pyrethroid insecticides were developed and characterized for the first time in this study by cold plasma-induced grafting polymerization using methacrylic acid as a functional monomer and cypermethrin (CYP) as a template. The nonimprinted membranes (NIMs) were also synthesized using the same procedure without the template. Meanwhile, AFM, XPS, ATR-FTIR, contact angle, and permselectivity experiments were conducted to elucidate the imprinting and recognition properties of MIMs. Results demonstrated that MIMs exhibited excellent imprinting effect and high permselectivity. A molecularly imprinted-membrane-assisted solvent extraction (MI-MASE) method based on the MIMs was established. The operating conditions were optimized for group-selective extraction of the five pyrethroid insecticides. Compared with NIMs, higher extraction recoveries (83.8% to 100.6%) of the five pyrethroid insecticides by gas chromatography-electron capture detector (GC-ECD) were obtained using MIMs at three spiked levels in fish samples; the RSD values were lower than 8.3%. The limits of detection (LOD) and quantification (LOQ) defined as the concentrations at which the signal-to-noise (S/N) ratio is 3:1 and 10:1, respectively, were in the range of 0.26 to 0.42 ?g/kg and 0.77 to 1.27 ?g/kg, respectively. No matrix effect of the developed MI-MASE was observed by gas chromatography/tandem mass spectrometry (GC/MS/MS). These results demonstrated a highly selective, efficient, and environment-friendly MI-MASE technique for preconcentration and purification of pyrethroid insecticides from seafood, followed by GC-ECD and GC/MS/MS. The excellent applicability and potential of MI-MASE for routine monitoring of pyrethroid pesticides in food samples has also been confirmed. PMID:25381696

Zhang, Rongrong; Guo, Xiaoqing; Shi, Xizhi; Sun, Aili; Wang, Lin; Xiao, Tingting; Tang, Zigang; Pan, Daodong; Li, Dexiang; Chen, Jiong

2014-12-01

118

Dual-component system dimethyl sulfoxide/LiCl as a solvent and catalyst for homogeneous ring-opening grafted polymerization of ?-caprolactone onto xylan.  

PubMed

The preparation of xylan-graft-poly(?-caprolactone) (xylan-g-PCL) copolymers was investigated by homogeneous ring-opening polymerization (ROP) in a dual-component system containing Lewis base LiCl and strong polar aprotic solvent dimethyl sulfoxide (DMSO). DMSO/LiCl acted as solvent, base, and catalyst for the ROP reaction. The effects of the parameters, including the reaction temperature, molar ratio of ?-caprolactone (?-CL) to anhydroxylose units (AXU) in xylan, and reaction time, on the degree of substitution (DS) and weight percent of PCL side chain (WPCL) were investigated. The results showed that xylan-g-PCL copolymers with low DS in the range of 0.03-0.39 were obtained under the given conditions. The Fourier transform infrared spectroscopy (FTIR), (1)H nuclear magnetic resonance (NMR), (13)C NMR, (1)H-(1)H correlation spectroscopy (COSY), and (1)H-(13)C correlation two-dimensional (2D) NMR [heteronuclear single-quantum coherence (HSQC)] characterization provided more evidence of the attachment of side chains onto xylan. Only one ?-CL was confirmed to be attached onto xylan with each side chain. Integration of resonances assigned to the substituted C2 and C3 in the HSQC spectrum also indicated 69.23 and 30.77% of PCL side chains attached to AXU at C3 and C2 positions, respectively. Although the attachment of PCL onto xylan led to the decreased thermal stability of xylan, the loss of unrecovered xylan fractions with low molecular weight because of the high solubility of xylan in DMSO/LiCl resulted in the increased thermal stability of the samples. This kind of xylan derivative has potential application in environmentally friendly and biodegradable materials considering the good biodegradability of xylan and PCL. PMID:24387806

Zhang, Xue-Qin; Chen, Ming-Jie; Liu, Chuan-Fu; Sun, Run-Cang

2014-01-22

119

Enhanced separation performance of PVDF/PVP-g-MMT nanocomposite ultrafiltration membrane based on the NVP-grafted polymerization modification of montmorillonite (MMT).  

PubMed

A novel hydrophilic nanocomposite additive (PVP-g-MMT), coupling of hydrophilic modifier, self-dispersant, and pore-forming agent (porogen), was synthesized by the surface modification of montmorillonite (MMT) with N-vinylpyrrolidone (NVP) via "grafting from" polymerization in the presence of H(2)O(2)-NH(3)·H(2)O as the initiator, and then the nanocomposite membrane of poly(vinylidene fluoride) (PVDF) and PVP-g-MMT was fabricated by wet phase inversion onto clean glass plates. The existence and dispersion of PVP-g-MMT had a great role on structures, morphologies, surface composition, and chemistry of the as-prepared nanocomposite membranes confirmed by varieties of spectroscopic and microscopic characterization techniques, all of which were the correlated functions of PVP-g-MMT content in casting solution. By using the dead-end filtration of protein aqueous solution, the performance of the membrane was evaluated. It was seen that all of the nanocomposite membranes showed obvious improvement of water flux and proper BSA rejection ratio, compared to the control PVDF membrane. Meanwhile, dynamic BSA fouling resistance and flux recovery properties were also greatly enhanced due to the changes of surface hydrophilicity and morphologies. All the experimental results indicated that the as-prepared PVDF nanocomposite membranes showed better separation performances than the control PVDF membrane. Hopefully, the demonstrated method of hydrophilic nanocomposite additive synthesis would be applied for commonly hydroxyl group-containing inorganic nanoparticles, which was favorable to fabricate hydrophilic nanoparticle-enhanced polymer membranes for water treatment. PMID:22376185

Wang, Panpan; Ma, Jun; Wang, Zhenghui; Shi, Fengmei; Liu, Qianliang

2012-03-13

120

Synthesis, characterization, and morphology study of poly(acrylamide-co-acrylic acid)-grafted-poly(styrene-co-methyl methacrylate) "raspberry"-shape like structure microgels by pre-emulsified semi-batch emulsion polymerization.  

PubMed

A novel microgels were polymerized using styrene (St), methyl methacrylate (MMA), acrylamide (AAm), and acrylic acid (AAc) monomers in the presence of N,N'-methylenebisacrylamide (MBA) cross-linker. Pre-emulsified monomer was first prepared followed by polymerizing monomers using semi-batch emulsion polymerization. Fourier Transform Infrared Spectroscopy (FTIR) and (1)H Nuclear Magnetic Resonance (NMR) were used to determine the chemical structure and to indentify the related functional group. Grafting and cross-linking of poly(acrylamide-co-acrilic acid)-grafted-poly(styrene-co-methyl methacrylate) [poly(AAm-co-AAc)-g-poly(St-co-MMA)] microgels are approved by the disappearance of band at 1300 cm(-1), 1200 cm(-1) and 1163 cm(-1) of FTIR spectrum and the appearance of CH peaks at 5.5-5.7 ppm in (1)H NMR spectrum. Scanning Electron Microscope (SEM) images indicated that poly(St-co-MMA) particle was lobed morphology coated by cross-linked poly(AAm-co-AAc) shell. Furthermore, SEM results revealed that poly(AAm-co-AAc)-g-poly(St-co-MMA) is composite particle that consist of "raspberry"-shape like structure core. Internal structures of the microgels showed homogeneous network of pores, an extensive interconnection among pores, thicker pore walls, and open network structures. Water absorbency test indicated that the sample with particle size 0.43 ?m had lower equilibrium water content, % than the sample with particle size 7.39 ?m. PMID:23123033

Ramli, Ros Azlinawati; Hashim, Shahrir; Laftah, Waham Ashaier

2013-02-01

121

Pre-irradiation-induced graft reaction of maleic anhydride onto polypropylene  

NASA Astrophysics Data System (ADS)

The radiation induced graft polymerization is a well-known method to obtain new materials. Until recently, only conventional radiation sources, such as Co-60 and electron beams, were used. Moreover, part of the damage induced in polymers by heavy ions can produce active sites (peroxides and hydroperoxides) that are useful to initiate grafting reactions. Maleic anhydride (MAH) was grafted onto polypropylene (PP) wax with a number-average molecular weight (Mn) of 8000 by gamma pre-irradiation technique. Effects of total dose, monomer concentration, reaction time, and temperature on percentage of grafting are studied in detail. It is shown that the optimum conditions for grafting are temperature of 70 degrees C and total dose of 14.4 kGy. PP-g-MAH is characterized by infrared spectrum. Differential scanning calorimetry shows that the compatibility of PP-g-MAH is better than that of PP.

Tan, X. M.; Xu, Y. S.; Wang, C. L.

2006-09-01

122

The Effects of Small amounts of Methanol on the Ionizing Radiation Induced Polymerization and Photopolymerization of Styrene.  

NASA Astrophysics Data System (ADS)

The mechanisms whereby ionizing radiation produce the species which initiate neutral free radical and ionic polymerization are investigated. Of particular interest is the remarkable enhancement effect on radiation induced polymerization of styrene by small concentrations of methanol. The approach is to compare the effects of methanol on the steady state polymerization of styrene induced by two different initiation methods: (1) gamma ray; (2) ultraviolet light (UV). In addition to these steady state reaction studies, microsecond pulse radiolysis with 6 MeV electrons is used to study the transient aspects of styrene polymerization and especially, the effect of methanol on the intiation step. The results for photopolymerization initiated with wavelengths above 280 nm, and therefore dominated by free radical polymerization, show that methanol has no sensitizing effect. This leads to eliminate the interaction between methanol and free radical in the initiation stage of a polymerization. By means of studies with different alcohols and an analysis of the dimer and trimer yield, a proton donor mechanism is successfully established for the enhancement effect of methanol on the radiation induced polymerization of styrene. The role of methanol is explained to serve as a rapid proton donor to the anion radical converting the latter to a neutral propagating free radical. The resulting methoxide anion then neutralizes the cation radical converting it to an additional neutral propagating free radical. Trace amounts of methanol (less than 0.05 M) in system with 2-3 mM water is found to have a desensitizing effect because of a quenching influence of methanol on propagating free ionic species; this effect is not observed in the water saturated (35 mM water) system or even at higher concentrations of methanol in the system with 3 mM water. In pulse radiolysis, a quantitative agreement between steady state polymerization and pulse radiolysis is for the first time obtained in the analysis of the radiation yield of propagating radicals. This agreement gives rise to quantitative values for the extinction coefficient of the carbon-center propagating free radical and the bimolecular rate constant for the termination reaction.

Tang, Fuh-Wei

1990-08-01

123

Structural characterization of radiation-grafted block copolymer films, using SANS technique  

Microsoft Academic Search

We report small-angle neutron scattering studies of grafted copolymer films of perfluorinated poly(ethylene propylene), FEP, base polymer and polystyrene, PS, grafted blocks. The films show highly anisotropic scattering patterns, revealing nematic-like ordering of the crystalline domain structure as a consequence of the processing conditions. Upon grafting, the styrene swells the amorphous domains in the copolymer formation. For styrene content beyond

Kell Mortensen; Urs Gasser; Selmiye Alkan Gürsel; Günther G. Scherer

2008-01-01

124

A contact angle investigation of the surface properties of selected proton-conducting radiation-grafted membranes  

Microsoft Academic Search

The surface and interfacial properties of proton-conducting ion-exchange membranes are quite important in their application as solid polymer electrolytes in fuel cells and other electrochemical devices. Radiation-grafted ion-exchange membranes based on poly(ethylene-alt-tetrafluoroethylene) (ETFE) and poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) films have been characterized by measuring the contact angles of several liquids on their surfaces at various stages in their preparation and as a

H. P Brack; M Wyler; G Peter; G. G Scherer

2003-01-01

125

RADIATION INDUCED BLOCK AND GRAFT COPOLYMERIZATION OF DISPERSION OF POLYMETHACRYLATES WITH ACRYLONITRILE  

Microsoft Academic Search

Graft and block copolymers were prepared by grafting acrylonitrile onto ; preirradiated aqueous dispersions of polymethylmethacrylate. The influence of ; different experimental conditions as irradiation time, dose rate, and the time ; between irradiation and addition to the monomer on the course of the reaction was ; studied in detail. Fractional precipitation of the copolymer showed no ; homopolymer acrylonitrile,

C. Schneider; J. Herz; D. Hummel

1962-01-01

126

Effect of gamma radiation on the mechanical and barrier properties of HEMA grafted chitosan-based films  

NASA Astrophysics Data System (ADS)

Chitosan films were prepared by dissolving 1% (w/v) chitosan powder in 2% (w/v) aqueous acetic acid solution. Chitosan films were prepared by solution casting. The values of puncture strength (PS), viscoelasticity coefficient and water vapor permeability (WVP) of the films were found to be 565 N/mm, 35%, and 3.30 g mm/m2 day kPa, respectively. Chitosan solution was exposed to gamma irradiation (0.1-5 kGy) and it was revealed that PS values were reduced significantly (p?0.05) after 1 kGy dose and it was not possible to form films after 5 kGy. Monomer, 2-hydroxyethyl methacrylate (HEMA) solution (0.1-1%, w/v) was incorporated into the chitosan solution and the formulation was exposed to gamma irradiation (0.3 kGy). A 0.1% (w/v) HEMA concentration at 0.3 kGy dose was found optimal-based on PS values for chitosan grafting. Then radiation dose (0.1-5 kGy) was optimized for HEMA grafting. The highest PS values (672 N/mm) were found at 0.7 kGy. The WVP of the grafted films improved significantly (p?0.05) with the rise of radiation dose.

Khan, Avik; Huq, Tanzina; Khan, Ruhul A.; Dussault, Dominic; Salmieri, Stephane; Lacroix, Monique

2012-08-01

127

Polymeric Materials With Additives for Durability and Radiation Shielding in Space  

NASA Technical Reports Server (NTRS)

Polymeric materials are attractive for use in space structures because of their light weight and high strength In addition, polymers are made of elements with low atomic numbers (Z), primarily carbon (C), hydrogen (H), oxygen (0), and nitrogen (N) which provide the best shielding from galactic cosmic rays (GCR) (ref. 1). Galactic cosmic rays are composed primarily of nuclei (i.e., fully ionized atoms) plus a contribution of about 2% from electrons and positrons. There is a small but significant component of GCR particles with high charge (Z > 10) and high energy (E >100 GeV) (ref. 2). These so-called HZE particles comprise only 1 to 2% of the cosmic ray fluence but they interact with very high specific ionization and contribute 50% of the long- term dose to humans. The best shield for this radiation would be liquid hydrogen, which is not feasible. For this reason, hydrogen-containing polymers make the most effective practical shields. Moreover, neutrons are formed in the interactions of GCR particles with materials. Neutrons can only lose energy by collisions or reactions with a nucleus since they are uncharged. This is a process that is much less probable than the Coulombic interactions of charged particles. Thus, neutrons migrate far from the site of the reaction in which they were formed. This increases the probability of neutrons reaching humans or electronic equipment. Fast neutrons (> 1 MeV) can interact with silicon chips in electronic equipment resulting in the production of recoil ions which can cause single event upsets (SEU) in sensitive components (ref. 3). Neutrons lose energy most effectively by elastic collisions with light atoms, particularly hydrogen atoms. Therefore, hydrogen-containing polymers are not only effective in interacting with GCR particles; they are also effective in reducing the energy of the neutrons formed in the interactions.

Kiefer, Richard

2011-01-01

128

Radiation grafting of oligo(ethylene glycol) ethyl ether methacrylate on polypropylene  

NASA Astrophysics Data System (ADS)

Oligo(ethylene glycol) ethyl ether methacrylate (OEGMA) can be grafted onto polypropylene (PP) films by post-irradiation grafting, forming a thermosensitive polymer layer, as indicated by FT-IR and contact angle measurements. In the first step, PP foils are irradiated by electron beam (5.5 kGy/min, up to 300 kGy) in the presence of air. Subsequently, the irradiated foils react with the monomer in oxygen-free solutions in isopropanol (up to 2 M of monomer) at 70 °C. Degree of grafting of OEGMA can be controlled by proper selection of absorbed dose, monomer concentration and reaction time. This work is a part of a broader project on thermosensitive materials facilitating cell growth and detachment for optimizing cell layer engineering techniques in the treatment of burn wounds.

Komasa, Justyna; Mi?ek, Andrzej; Ula?ski, Piotr; Rosiak, Janusz M.

2014-01-01

129

Temperature-sensitive polypropylene membranes prepared by plasma polymerization  

Microsoft Academic Search

Poly-N-isopropylacylamide (PNIPAAm) was grafted on polypropylene (PP) microfiltration membranes using plasma polymerization. The surface of the grafted membrane was evaluated by Fourier transform infrared (FTIR) spectroscopy. Scanning electron microscopy pictures demonstrated that the PNIPAAm can be grafted either on the surface or in the pores of the membrane. The morphology of the grafted membrane can be adjusted through monomer concentration

Liang Liang; Mingkung Shi; Vilayanur V. Viswanathan; Loni M. Peurrung; James S. Young

2000-01-01

130

Grafting of Branched Polymers onto Carbon Black Surface: Radical Postpolymerization Initiated by Pendant Azo Groups of Grafted Polymer on the Surface  

Microsoft Academic Search

The grafting of highly branched polymer onto carbon black surface by postpolymerization of glycidyl methacrylate (GMA) initiated by pendant azo groups introduced to grafted polyGMA on the surface was investigated. The graft polymerization of GMA onto carbon black was achieved by use of azo groups introduced onto the surface: the percentage of grafting (the proportion of grafted polymer to carbon

Shinji Hayashi; Takamitsu Iida; Norio Tsubokawa

1997-01-01

131

Gamma-ray co-irradiation induced graft polymerization of NVP and SSS onto polypropylene non-woven fabric and its blood compatibility  

NASA Astrophysics Data System (ADS)

Sodium styrenesulfonate was grafted onto PPNWF via ?-ray co-irradiation method with the existence of N-vinyl-2-pyrrolidone. The effect of absorbed dose, dose rate and concentration of binary monomer on the degree of grafting was investigated. The surface chemical change was characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The wettability was characterized through the measurement of adsorption percentage of water and phosphate buffer solution (PBS). The result demonstrated that the grafted poly(NVP-co-SSS) chains can improve the hydrophilicity of PPNWF. Furthermore, the modified PPNWF has good blood compatibility, such as low hemolysis rate, low platelet adhesion and effectively extending the blood coagulation times. Consequently, hydrophilicity and hemocompatibility of PPNWF were greatly enhanced by the immobilization of poly(NVP-co-SSS) chains.

Li, Rong; Wang, Hengdong; Wang, Wenfeng; Ye, Yin

2013-10-01

132

Introduction of anticoagulation group to polypropylene film by radiation grafting and its blood compatibility  

NASA Astrophysics Data System (ADS)

Based on in vitro tests for an improvement of the blood compatibility of polypropylene (PP) films by grafting O-butyrylchitosan (OBCS), we prepared a novel biocompatible film. The immobilization was accomplished by irradiating with ultraviolet light, OBCS being coated on the film surface to photolyze azide groups, thus cross-linking OBCS and PP together. The grafted sample films were verified by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), electron spectroscopy for chemical analysis (ESCA) and the water contact angle measurements. The blood compatibility of the OBCS-grafted PP films was evaluated by platelet rich plasma (PRP) contacting experiments and protein adsorption experiments using blank PP film as the control. It demonstrated that blood compatibility of the OBCS-grafted surfaces is better than that of the blank PP. The suitable modifications could be carried out to tailor PP biomaterial to meet the specific needs of different biomedical applications. These results suggest that the photocrosslinkable chitosan developed here has the potential of serving as a new biomaterial in medical use.

Mao, Chun; Zhang, Can; Qiu, Yongzhi; Zhu, Aiping; Shen, Jian; Lin, Sicong

2004-04-01

133

Evaluation of Thermal Control Coatings and Polymeric Materials Exposed to Ground Simulated Atomic Oxygen and Vacuum Ultraviolet Radiation  

NASA Technical Reports Server (NTRS)

Numerous thermal control and polymeric samples with potential International Space Station applications were evaluated for atomic oxygen and vacuum ultraviolet radiation effects in the Princeton Plasma Physics Laboratory 5 eV Neutral Atomic Oxygen Facility and in the MSFC Atomic Oxygen Drift Tube System. Included in this study were samples of various anodized aluminum samples, ceramic paints, polymeric materials, and beta cloth, a Teflon-impregnated fiberglass cloth. Aluminum anodizations tested were black duranodic, chromic acid anodize, and sulfuric acid anodize. Paint samples consisted of an inorganic glassy black paint and Z-93 white paint made with the original PS7 binder and the new K2130 binder. Polymeric samples evaluated included bulk Halar, bulk PEEK, and silverized FEP Teflon. Aluminized and nonaluminized Chemfab 250 beta cloth were also exposed. Samples were evaluated for changes in mass, thickness, solar absorptance, and infrared emittance. In addition to material effects, an investigation was made comparing diffuse reflectance/solar absorptance measurements made using a Beckman DK2 spectroreflectometer and like measurements made using an AZ Technology-developed laboratory portable spectroreflectometer.

Kamenetzky, R. R.; Vaughn, J. A.; Finckenor, M. M.; Linton, R. C.

1995-01-01

134

Poly (acryloyl- L-proline methyl ester) hydrogels obtained by radiation polymerization for the controlled release of drugs  

NASA Astrophysics Data System (ADS)

Thermosensitive hydrogels were obtained by radiation-induced polymerization of acryloyl- L-proline methyl ester in the presence of a crosslinking agent. The measurements of equilibrium water content in the temperature range between 0° and 60°C showed that the samples swelled at low temperatures while they shrank at high temperatures. These hydrogels were used as drug delivery systems for the controlled release of insulin. In vivo studies carried out on diabetic rats ascertained a significant reduction in the hyperglycemic level in the blood which continued for about 2 months.

Carenza, M.; Caliceti, P.; Veronese, F. M.; Martellini, F.; Higa, O. Z.; Yoshida, M.; Katakai, R.

2000-03-01

135

Surface modification of polyethylene by radiation-induced grafting for adhesive bonding. V. Comparison with other surface treatments. [Gamma radiation  

Microsoft Academic Search

Helium gas plasma treatment of low-density polyethylene (LDPE) yields much lower peel strength than oxidative treatment using chromic acid and oxygen gas plasma. The practical adhesion, the bondability retention, and the bond durability of oxidatively treated LDPE sheets, bonded with epoxy adhesives, have been compared with those of partially hydrolyzed LDPE-methyl acrylate surface grafts. The oxidized surfaces easily lose the

S. Yamakawa; F. Yamamoto

1980-01-01

136

Surface modification of polyethylene by radiation-induced grafting for adhesive bonding. V. Comparison with other surface treatments. [Gamma radiation  

SciTech Connect

Helium gas plasma treatment of low-density polyethylene (LDPE) yields much lower peel strength than oxidative treatment using chromic acid and oxygen gas plasma. The practical adhesion, the bondability retention, and the bond durability of oxidatively treated LDPE sheets, bonded with epoxy adhesives, have been compared with those of partially hydrolyzed LDPE-methyl acrylate surface grafts. The oxidized surfaces easily lose the bondability by light rubbing with tissue paper, solvent extraction, heat aging, and artificial weathering, whereas the grafted surfaces retain the bondability. The bondability loss is due to removal of the oxidized layer, and the bondability retention is due to retention of the surface homopolymer layer. Conventional antioxidants stabilize the grafted but not the oxidized surfaces against thermal oxidative degradation. The grafted LDPE joints have much higher bond durability in humid environments than those of the oxidized LDPE joints. The dry and wet peel strengths of oxidized LDPE joints are greatly improved by application of primers consisting of a base epoxy resin and organic solvents. An adhesion mechanism involving penetration of epoxy adhesives into the oxidized layers and subsequent reinforcement of the layers by curing of the penetrated epoxy is proposed. 5 figures, 5 tables.

Yamakawa, S.; Yamamoto, F.

1980-01-01

137

Surface Morphology of Radiation-Grafted Binary Copolymers Measured in Buffer Solution under Swelling Condition  

NASA Astrophysics Data System (ADS)

pH-dependent binary graft copolymers, [polypropylene (PP)-g-2-(dimethylamino)ethylmethacrylate (DMAEMA)-g-N-isopropylacrylamide (NIPAAm) and (PP-g-4-vinylpyridine (4VP))-g-NIPAAm], synthesized by a two-step gamma-irradiation method, were characterized in terms of surface morphology under swelling condition. A confocal laser microscope with a water-immersion objective lens was employed for noncontact surface profile measurement of an extremely soft surface. Surface morphology was significantly different between these two binary copolymers, suggesting that the surface morphology of the binary copolymer reflected that of the first graft layer. Surface roughness was also analyzed as a function of the pH of the swelling buffer solution. Surface roughness increased with swelling ratio, and it further increased at lower pH, consistent with the results of a swelling ratio experiment previously reported.

Meléndez-Ortiz, Hector Ivan; Bucio, Emilio; Isoshima, Takashi; Ito, Hiromi; Hara, Masahiko

2010-01-01

138

Fire proofing by radiation grafting (application on polyester and polypropylene). Scientific technical report  

SciTech Connect

This report outlines efforts to try out a modern technique, radition grafting, rather than chemical and heat fixation, to make textiles more fire-proof by reducing as much as possible the deterioration in conventional properties, in particular softness and handle, to which the former give rise. The expected consequences are twofold: possession of a general method for fire-proofing textile materials which retain the conventional initial characteristics more fully, and improvement of the durability of the fire-proof properties.

Hill, B.J.; Einsele, U.; Di Modica, G.; Wattiez, D.

1980-01-01

139

Mechanical properties of tough hydrogels synthesized with a facile simultaneous radiation polymerization and cross-linking method  

NASA Astrophysics Data System (ADS)

Radiation-induced polymerization and cross-linking method has been applied to hydrogel preparations for decades, but less attention has been paid to the mechanical properties of the hydrogels. In this work, we provide a systematic study on the mechanical properties of hydrogels synthesized with the simultaneous radiation polymerization and cross-linking method. The prepared polyacrylamide (PAAm) had very good mechanical properties, namely high compressive strengths (several to more than 10 MPa), high tensile strengths (up to 260 kPa), high fracture strains (up to 12) and high fracture energies (10-160 J/m2). Absorbed dose and monomer concentration were the two important factors affecting the mechanical properties of the gels. The compressive strength and elastic modulus of the gels increased with increasing absorbed dose and monomer concentration, while the tensile strength, fracture strain and fracture energy of the gels decreased with increasing absorbed dose. The gels also showed excellent elastic recovery property, as indicated by the low stress-strain hysteresis ratios in cyclic tensile tests as well as the small loss factors measured with dynamic mechanical analysis (DMA).

Jiang, Fangzhi; Wang, Xuezhen; He, Changcheng; Saricilar, Sureyya; Wang, Huiliang

2015-01-01

140

New trends of radiation processing applications  

NASA Astrophysics Data System (ADS)

Major fields of radiation processing applications are: polymeric materials, food processing, sterilization of medical products and environmental conservation. There are about 200 60Co gamma irradiation facilities and 700 electron beam accelerators, mainly for commercial purposes, throughout the world. Radiation cross-linking and grafting techniques of polymeric materials have been providing many unique products including heat materials, heat shrinkable materials, curing of coatings and battery separators. Extensive studies have been devoted to the development of bio-medical materials using radiation processing to prepare bio-compatible materials and controlled release of drugs. New wound dressings have been successfully developed in Poland and Israel for commercial clinical use.

Machi, Sueo

1996-03-01

141

Preparation of chitosan/poly(butyl acrylate) hybrid materials by radiation-induced graft copolymerization based on phthaloylchitosan  

NASA Astrophysics Data System (ADS)

Graft copolymerization of butyl acrylate onto chitosan via phthaloylchitosan intermediate has been examined. Because the intermediate phthaloylchitosan was soluble in organic solvents, the graft copolymerization can be carried out efficiently in homogeneous system. Under appropriate irradiation dose and concentration of butyl acrylate monomer, the grafting percentage reached 838%. The graft copolymers exhibited high swelling not only in aqueous acid but also in organic solvents. Due to the poly(butyl acrylate) side chains, the resulting graft copolymers exhibited glass transition phenomena and showed improved thermal stability.

Li, Yu; Liu, Li; Shen, Xiaofeng; Fang, Yue-e.

2005-12-01

142

Optimization of reaction parameters of radiation induced grafting of 1-vinylimidazole onto poly(ethylene-co-tetraflouroethene) using response surface method  

NASA Astrophysics Data System (ADS)

Radiation induced grafting of 1-vinylimidazole (1-VIm) onto poly(ethylene-co-tetraflouroethene) (ETFE) was investigated. The grafting parameters such as absorbed dose, monomer concentration, grafting time and temperature were optimized using response surface method (RSM). The Box-Behnken module available in the design expert software was used to investigate the effect of reaction conditions (independent parameters) varied in four levels on the degree of grafting ( G%) (response parameter). The model yielded a polynomial equation that relates the linear, quadratic and interaction effects of the independent parameters to the response parameter. The analysis of variance (ANOVA) was used to evaluate the results of the model and detect the significant values for the independent parameters. The optimum parameters to achieve a maximum G% were found to be monomer concentration of 55 vol%, absorbed dose of 100 kGy, time in the range of 14-20 h and a temperature of 61 °C. Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to investigate the properties of the obtained films and provide evidence for grafting.

Nasef, Mohamed Mahmoud; Aly, Amgad Ahmed; Saidi, Hamdani; Ahmad, Arshad

2011-11-01

143

Development of high-productivity, strong cation-exchange adsorbers for protein capture by graft polymerization from membranes with different pore sizes  

PubMed Central

This paper describes the surface modification of macroporous membranes using ATRP (atom transfer radical polymerization) to create cation-exchange adsorbers with high protein binding capacity at high product throughput. The work is motivated by the need for a more economical and rapid capture step in downstream processing of protein therapeutics. Membranes with three reported nominal pore sizes (0.2, 0.45, 1.0 ?m) were modified with poly(3-sulfopropyl methacrylate, potassium salt) tentacles, to create a high density of protein binding sites. A special formulation was used in which the monomer was protected by a crown ether to enable surface-initiated ATRP of this cationic polyelectrolyte. Success with modification was supported by chemical analysis using Fourier-transform infrared spectroscopy and indirectly by measurement of pure water flux as a function of polymerization time. Uniformity of modification within the membranes was visualized with confocal laser scanning microscopy. Static and dynamic binding capacities were measured using lysozyme protein to allow comparisons with reported performance data for commercial cation-exchange materials. Dynamic binding capacities were measured for flow rates ranging from 13 to 109 column volumes (CV)/min. Results show that this unique ATRP formulation can be used to fabricate cation-exchange membrane adsorbers with dynamic binding capacities as high as 70 mg/mL at a throughput of 100 CV/min and unprecedented productivity of 300 mg/mL/min. PMID:23175597

Chenette, Heather C.S.; Robinson, Julie R.; Hobley, Eboni; Husson, Scott M.

2012-01-01

144

Prospectively versus Retrospectively ECG-Gated 256-Slice CT Angiography to Assess Coronary Artery Bypass Grafts — Comparison of Image Quality and Radiation Dose  

PubMed Central

Objective In this retrospective non-randomized cohort study, the image quality and radiation dose were compared between prospectively electrocardiogram (ECG)-gated axial (PGA) and retrospectively ECG-gated helical (RGH) techniques for the assessment of coronary artery bypass grafts using 256-slice CT. Methods We studied 124 grafts with 577 segments in 64 patients with a heart rate (HR) <85 bpm who underwent CT coronary angiography (CTCA); 34 patients with RGH-CTCA and 30 patients with PGA-CTCA. The image quality of the bypass grafts was assessed by a 5-point scale (1?=?excellent to 5?=?non-diagnostic) for each segment (proximal anastomosis, proximal, middle, distal course of graft body, and distal anastomosis). Other objective image quality indices such as noise, signal-to-noise ratio (SNR) and contrast-to-noise ratios (CNR) were assessed. Radiation doses were also compared. Results Patient characteristics of the two groups were well matched except HR. The HR of the PGA group was lower than that of the RGH group (62.0±5.0 vs. 65.7±7.4). For both groups, over 90% of segments received excellent or good image quality scores and none was non-evaluative. The image quality generally degraded as graft segment approached to distal anastomosis regardless of techniques and graft types. Image quality scores of the PGA group were better than those of the RGH group (1.51±0.53 vs. 1.73±0.62; p<0.001). There was no significantly difference of objective image quality between two techniques, and the effective radiation dose was significantly lower in the PGA group (7.0±1.2 mSv) than that of the RGH group (20.0±4.6 mSv) (p<0.001), with a 65.0% dose reduction. Conclusions Following bypass surgery, 256-slice PGA-CTCA is superior to RGH-CTCA in limiting the radiation dose and obtaining better image quality for bypass grafts. PMID:23145126

Lee, Yi-Wei; Yang, Ching-Ching; Mok, Greta S. P.; Law, Wei-Yip; Su, Cheng-Tau; Wu, Tung-Hsin

2012-01-01

145

Investigation of space radiation effects in polymeric film-forming materials  

NASA Technical Reports Server (NTRS)

The literature search in the field of ultraviolet radiation effects that was conducted during the previous program, Contract No. NAS1-12549, has been expanded to include the effects of charged particle radiation and high energy electromagnetic radiation. The literature from 1958 to 1969 was searched manually, while the literature from 1969 to present was searched by using a computerized keyword system. The information generated from this search was utilized for the design of an experimental program aimed at the development of materials with improved resistance to the vacuum-radiation environment of space. Preliminary irradiation experiments were performed which indicate that the approaches and criteria employed are very promising and may provide a solution to the challenging problem of polymer stability to combined ultraviolet/high energy radiation.

Giori, C.; Yamauchi, T.; Jarke, F.

1975-01-01

146

Radiation-induced and RAFT-mediated grafting of poly(hydroxyethyl methacrylate) (PHEMA) from cellulose surfaces  

NASA Astrophysics Data System (ADS)

This paper presents the results of RAFT mediated free-radical graft copolymerization of 2-hydroxyethyl methacrylate (HEMA) onto cellulose fibers in a "grafting-from" approach under ?-irradiation. The effects of absorbed dose and monomer concentration on the graft ratios were investigated at different monomer (HEMA) to RAFT agent (cumyl dithiobenzoate, CDB) ratios. Cellulose-g-PHEMA copolymers with various graft ratios up to 92% (w/w) have been synthesized. The synthesized copolymers were characterized by ATR-FTIR spectroscopy, X-ray photoelectron spectroscopy, elemental analysis and scanning electron microscopy. The results of various techniques confirmed the existence of PHEMA in the copolymer composition.

Kodama, Yasko; Barsbay, Murat; Güven, Olgun

2014-01-01

147

Prospective versus retrospective ECG-gated 64-detector coronary CT angiography for evaluation of coronary artery bypass graft patency: comparison of image quality, radiation dose and diagnostic accuracy  

Microsoft Academic Search

We aimed to evaluate image quality, radiation dose and diagnostic accuracy of coronary CT angiography (CCTA) with a prospectively\\u000a gated transverse-axial scan (PGT) compared with a retrospectively gated helical scan (RGH), using a 64-slice scanner in patients\\u000a who underwent coronary artery bypass graft (CABG). Of the 131 consecutive patients that underwent CABG using 64-slice multidetector\\u000a row computed tomography during 2008,

Jae Hwan Lee; Eun Ju Chun; Sang Il Choi; Mani Vembar; Cheong Lim; Kay-Hyun Park; Dong-Ju Choi

148

Synthesis and characterization of photoluminescent hybrids of poly( ?-caprolactone)-grafted-polyhedral oligosilsesquioxane by using a combination of ring-opening polymerization and click chemistry  

NASA Astrophysics Data System (ADS)

Photoluminescent hybrids of poly( ?-caprolactone) (PCL), polyhedral oligosilsesquioxane (POSS) and terbium ions (Tb3+) were synthesized by using a combination of ring-opening polymerization (ROP), click chemistry and coordination chemistry. Initially, acetylene functionalized PCL (alkyne-PCL-COOH) was prepared by using ROP of ?-caprolactone with propargyl alcohol, and azide-substituted POSS (POSS-N3) was prepared by using the reaction of chloropropyl-heptaisobutyl-substituted POSS with NaN3. The click reaction between alkyne-PCL-COOH and POSS-N3 afforded POSS-g-PCL, which was subsequently coordinated with Tb3+ ions in the presence of 1,10-phenanthroline to produce POSS-g-PCL-Tb3+-Phen. The structures and compositions of the hybrids were investigated by using 1H nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), Field emission scanning electron microscope (FE-SEM), Transmission electron microscopy (TEM), and Thermogravimetric analysis (TGA). The optical properties of POSS-g-PCL-Tb3+-Phen complexes were characterized by using photoluminescence spectroscopy, which showed four high emission bands centered at 489, 545, 584, and 620 nm with excitation at 330 nm. The emission spectra of the europium-ion-coordinated hybrids, POSS-g-PCL-Eu3+-Phen, had four high-intensity peaks, 594, 617, 652 and 686 nm, for an excitation wavelength of 352 nm.

Cao, Xuan Thang; Showkat, Ali Md; Bach, Long Giang; Jeong, Yeon Tae; Kim, Jong Soo; Lim, Kwon Taek; Gal, Yeong-Soon

2015-01-01

149

Novel polymeric elastomers for actuation  

Microsoft Academic Search

Efficient actuators that are lightweight, high performance and compact are needed to support telerobotic requirements for future NASA missions. A new class of electrostrictive polymeric materials has been developed in our recent work. The materials are graft elastomers that exhibit not only large electric field-induced strain (4%) but also a relatively high mechanical modulus (560 MPa). Consequently, the materials offer

J. Su; J. S. Harrison; T. St Clair

2000-01-01

150

Thermal analysis evaluation of mechanical properties changes promoted by gamma radiation on surgical polymeric textiles  

NASA Astrophysics Data System (ADS)

The large number of surgical operations with post-operative infection problems and the appearing of new infectious diseases, contribute to the development of new materials in order to answer the needs of health care services. This development must take into account the modifications promoted by sterilisation methods in materials, namely by gamma radiation. The differential scanning calorimetry (DSC) and thermogravimetry (TGA) techniques show that a nonwoven and a laminate textiles maintain a good molecular cohesion, do not showing high levels of degradation, for gamma radiation dose values lower than 100 kGy in nonwoven and 200 kGy in laminate materials. The tensile strength and the elongation decrease slowly for the nonwoven textile and decrease faster for the laminate textile for 25 and 80 kGy absorbed dose. This paper shows that the DSC and TGA techniques can be helpful for the prevision of mechanical changes occurred in the materials as a consequence of the gamma irradiation.

Ferreira, L. M.; Casimiro, M. H.; Oliveira, C.; Cabeço Silva, M. E.; Marques Abreu, M. J.; Coelho, A.

2002-05-01

151

The effect of nanocomposite polymeric layer on the radiation of antisymmetric zero-order Lamb wave in a piezoelectric plate contacting with liquid  

NASA Astrophysics Data System (ADS)

A nanocomposite polymeric layer is proposed to be used for increasing the efficiency of ultrasound radiation into the liquid by antisymmetric zero-order (A0) Lamb waves propagating in piezoelectric plates. The theoretical and experimental investigations of the influence of the nanocomposite polymeric layers on the efficiency and radiation angle of acoustic wave into liquid were carried out. It has been theoretically shown that the use of the layer of the polyethylene of low density with nanoparticles of cadmium sulfide of concentration 25% between the plate of 128YX LiNbO3 and water medium allows to increase the radiation attenuation on ˜1 dB/? if the ratio of the thicknesses of the layer and plate is equal to 0.16 at the frequency of 1.3 MHz. The experimental data were in a good agreement with theoretical results. It has been also shown that the presence of nanocomposite film leads to the increase of the radiation angle of bulk acoustic wave in liquid and allows the effective operation of the radiator not only in the sweet water but also in salt one. The obtained results may be used for the development of effective radiators/receivers of acoustic waves in liquids for flow meters and for underwater communication systems.

Kuznetsova, I. E.; Zaitsev, B. D.; Borodina, I. A.; Shikhabudinov, A. M.; Teplykh, A. A.; Manga, E.; Feuillard, G.

2013-06-01

152

Skin Graft  

PubMed Central

Skin graft is one of the most indispensable techniques in plastic surgery and dermatology. Skin grafts are used in a variety of clinical situations, such as traumatic wounds, defects after oncologic resection, burn reconstruction, scar contracture release, congenital skin deficiencies, hair restoration, vitiligo, and nipple-areola reconstruction. Skin grafts are generally avoided in the management of more complex wounds. Conditions with deep spaces and exposed bones normally require the use of skin flaps or muscle flaps. In the present review, we describe how to perform skin grafting successfully, and some variation of skin grafting. PMID:22570780

Shimizu, Ruka; Kishi, Kazuo

2012-01-01

153

Temperature-sensitive porous membrane production through radiation co-grafting of NIPAAm on/in PVDF porous membrane  

NASA Astrophysics Data System (ADS)

N-isopropylacrylamide (NIPAAm) monomer was grafted on and in poly(vinylidene fluoride) (PVDF) micro-pore membrane by ?-irradiation. The influence of irradiation and reaction conditions on the grafting yield was investigated in detail. The chemical structure of NIPAAm-grafted PVDF (NIPAAm-g-PVDF) membrane was characterized by Fourier transform infrared spectra and X-ray photoelectron spectra measurements. The morphology of the sample surface as well as the cross-section before and after grafting was characterized by scanning electron microscope. The temperature sensitive properties of the membrane were monitored by measuring the conductance as well as the water flux through the sample thickness. The results show that the membrane exhibits clearly temperature-sensitive permeability to water as expected, i.e. the permeability of water changes dramatically as the temperature goes over the lower critical solution temperature of NIPAAm.

Liu, Qi; Zhu, Zhiyong; Yang, Xiaomin; Chen, Xiliang; Song, Yufeng

2007-04-01

154

Effects of Electrons, Protons, and Ultraviolet Radiation on Thermophysical Properties of Polymeric Films  

NASA Technical Reports Server (NTRS)

The response of coated thin polymer films to ultraviolet (UV), electron and proton radiation simultaneously has been evaluated, with selected measurements in situ. Exposure was intended to simulate the electron and proton radiation environment near the Earth-Sun Lagrangian points (LI and L2) for five years and approximately 1000 equivalent solar hours (ESH) UV. These orbital environments are relevant to several potential missions such as the Next Generation Space Telescope and Geomagnetic Storm Warning, both of which may use thin film based structures for a sunshade and solar sail, respectively. The thin film candidates (12.5 micrometers thick) consisted of commercially available materials (Kapton(R) E, HN, Upilex(R) S, CP-1, CP-2, TOR-RC, and TOR-LMBP) that were metalized on one side with vapor deposited aluminum. All of the films are aromatic polyimides, with the exception of TORLMBP, which is a copoly(arylene ether benzimidazole). The films were exposed as second surface mirrors and the effects of the exposure on solar absorptance, thermal emittance, and tensile properties were determined. The in situ changes in solar absorptance from Kapton(R) and Upilex(R) were less than 0. 1, whereas the solar absorptance of TOR and CP films increased by more than 0.3 without saturating. The thermal emittance measurements also showed that the Kapton(R) and Upilex(R) materials increased only 1-2%, but the remaining materials increased 5-8%. Based on tensile property measurements made in air following the test, the failure stress of every type of polymer film decreased as a result of irradiation. The polymers most stable in reflectance, namely Upilex(R) and Kapton(R), were also the strongest in tension before irradiation, and they retained the greatest percentage of tensile strength. The films less stable in reflectance were also weaker in tension, and lost more tensile strength as a result of irradiation. The apparent failure strain (as a percent of original gage length) of every type of polymer film except TOR-RC, decreased as a result of irradiation.

Russell, Dennis A.; Connell, John W.; Fogdall, Lawrence B.; Winkler, Werner W.

2001-01-01

155

Uranium Recovery from Seawater: Development of Fiber Adsorbents Prepared via Atom-Transfer Radical Polymerization  

SciTech Connect

A novel adsorbent preparation method using atom-transfer radical polymerization (ATRP) combined with radiation-induced graft polymerization (RIGP) was developed to synthesize an adsorbent for uranium recovery from seawater. The ATRP method allowed a much higher degree of grafting on the adsorbent fibers (595 2818%) than that allowed by RIGP alone. The adsorbents were prepared with varied composition of amidoxime groups and hydrophilic acrylate groups. The successful preparation revealed that both ligand density and hydrophilicity were critical for optimal performance of the adsorbents. Adsorbents synthesized in this study showed a relatively high performance (141 179 mg/g at 49 62 % adsorption) in laboratory screening tests using a uranium concentration of ~6 ppm. This performance is much higher than that of known commercial adsorbents. However, actual seawater experiment showed impeded performance compared to the recently reported high-surface-area-fiber adsorbents, due to slow adsorption kinetics. The impeded performance motivated an investigation of the effect of hydrophilic block addition on the graft chain terminus. The addition of hydrophilic block on the graft chain terminus nearly doubled the uranium adsorption capacity in seawater, from 1.56 mg/g to 3.02 mg/g. The investigation revealed the importance of polymer chain conformation, in addition to ligand and hydrophilic group ratio, for advanced adsorbent synthesis for uranium recovery from seawater.

Saito, Tomonori [ORNL; Brown, Suree [ORNL; Chatterjee, Sabornie [ORNL; Kim, Jungseung [ORNL; Tsouris, Costas [ORNL; Mayes, Richard T [ORNL; Kuo, Li-Jung [Pacific Northwest National Laboratory (PNNL); Gill, Gary [Pacific Northwest National Laboratory (PNNL); Oyola, Yatsandra [ORNL; Janke, Christopher James [ORNL; Dai, Sheng [ORNL

2014-01-01

156

Engineering Polymeric Scaffolds for Bone Grafts  

Microsoft Academic Search

Orthopedic injuries resulting from trauma or improper development often require surgical intervention to restore natural tissue function. Currently, over one million operations are performed annually for the surgical reconstruction of bone [50]. The well-known limitations associated with autografts, allografts, and bone cements have led to the investigation of synthetic polymers as support matrices for bone tissue engineering. Polymers are long-chain

Martha W. Betz; Diana M. Yoon; John P. Fisher

157

Chemical and physical modifications of silicone for novel vascular grafts  

Microsoft Academic Search

The thrombogenecity of synthetic vascular grafts can be improved by applying a quiescent monolayer of endothelial cells on the graft surface. Whereas most investigations have focused on chemically modifying polymeric materials to promote endothelial cell adhesion, the approach in this thesis is to use micro-scale patterns of grooves, consisting of parallel ridges and channels, on a model silicone template to

Pimporn Uttayarat

2007-01-01

158

Structure-function properties of starch spherulites grafted with poly(methyl acrylate)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Spherulites, produced by steam jet-cooking high-amylose starch and oleic acid, were grafted with methyl acrylate, both before and after removal of un-complexed amylopectin. For comparison, granular high-amylose corn starch was graft polymerized in a similar manner. The amount of grafted and ungrafte...

159

Laundering durable antibacterial cotton fabrics grafted with pomegranate-shaped polymer wrapped in silver nanoparticle aggregations  

PubMed Central

To improve the laundering durability of the silver functionalized antibacterial cotton fabrics, a radiation-induced coincident reduction and graft polymerization is reported herein where a pomegranate-shaped silver nanoparticle aggregations up to 500?nm can be formed due to the coordination forces between amino group and silver and the wrapping procedure originated from the coincident growth of the silver nanoparticles and polymer graft chains. This pomegranate-shaped silver NPAs functionalized cotton fabric exhibits outstanding antibacterial activities and also excellent laundering durability, where it can inactivate higher than 90% of both E. coli and S. aureus even after 50 accelerated laundering cycles, which is equivalent to 250 commercial or domestic laundering cycles. PMID:25082297

Liu, Hanzhou; Lv, Ming; Deng, Bo; Li, Jingye; Yu, Ming; Huang, Qing; Fan, Chunhai

2014-01-01

160

Microwave assisted synthesis and characterization of acrylamide grafted gellan, application in drug delivery.  

PubMed

The synthesis of acrylamide-grafted-gellan gum was carried out by microwave-assisted free radical polymerization using cerric ammonium nitrate (CAN) as redox initiator. A series of graft copolymers, varying in amount of acrylamide, CAN and microwave irradiation time was prepared. The modified gum was extracted with 20% (v/v) methanol to remove the homopolymer formed during polymerization reaction. These graft copolymers were characterized by FTIR, (13)C NMR, CHN, SEM, rheological studies and DSC studies. Comparison of grafting parameters such as grafting efficiency, percentage grafting and percentage conversion were carried out among various series of graft copolymers and then correlating it with elemental analysis, DSC, viscosity results. The acute oral toxicity study of grated gum was evaluated as per OECD guideline. Tablets were prepared by incorporating antidiabetic drug metformin hydrochloride (MTF) in grafted gum along with excipients. In vitro studies were performed on prepared tablet formulations showing release up to 8 h. PMID:24751070

Vijan, Veena; Kaity, Santanu; Biswas, Soumen; Isaac, Jinu; Ghosh, Animesh

2012-09-01

161

Synthesis, characterization and thermal sensitivity of chitosan-based graft copolymers  

Microsoft Academic Search

Novel chitosan-based graft copolymers (CECTS-g-PDMA) were synthesized through homogeneous graft copolymerization of (N,N-dimethylamino)ethyl methacrylate (DMA) onto N-carboxyethylchitosan (CECTS) in aqueous solution by using ammonium persulfate (APS) as the initiator. The effect of polymerization variables, including initiator concentration, monomer concentration, reaction time and temperature, on grafting percentage was studied. XRD, FTIR, DSC and TGA were used to characterize the graft copolymers.

Hong-Mei Kang; Yuan-Li Cai; Peng-Sheng Liu

2006-01-01

162

One-pot synthesis of colloidal nanobowls and hybrid multipod-like nanoparticles by radiation miniemulsion polymerization.  

PubMed

A facile approach is proposed to one-pot synthesis of two kinds of nanoparticles: a new type of PS nanobowls (a hole appearing at the bottom of nanobowl) and PS/silica hybrid multipod-like nanoparticles. The two type of nanoparticles generated together during polymerization could be separated easily by centrifugation. Furthermore, the structure of nanobowls could be easily controlled by the weight ratio of monomer/silica. In addition, we find that the multipod-like nanoparticles play important roles in hydrophobic properties. The water contact angle increased from 24.0° to 143.3° after coated with the multipod-like nanoparticles. PMID:21823186

Ge, Xueping; Ge, Xuewu; Wang, Mozhen; Liu, Huarong; Fang, Bin; Li, Zhi; Shi, Xiaojun; Yang, Cunzhong; Li, Guang

2011-10-18

163

Kinetic approach to radiation-induced grafting in the polyethylene-styrene system. IV. Comparison between high density polyethylene and low density polyethylene. [Gamma radiation  

SciTech Connect

The investigation method reported in earlier articles was applied to preirradiation methods of the reaction of low-density polyethylene (LDPE) in liquid and vapor and compared with high-density polyethylene (HDPE). Monomer concentrations during reactions and monomer feed rates were determined gravimetrically. Increasing patterns of the degree of grafting were obtained and compared. Monomer concentration during the reactions was lower in LDPE than HDPE and radical decay was more rapid in LDPE. A model calculation was applied to this experiment and a schematic explanation was attempted. The differences between the reaction mechanisms of HDPE and LDPE are explained.

Imai, M.

1981-07-01

164

Use of dermal-fat grafts in the post-oncological reconstructive surgery of atrophies in the zygomatic region: clinical evaluations in the patients undergone to previous radiation therapy  

PubMed Central

Introduction Grafting of autologous adipose tissue can be recommended in some cases of facial plastic surgery. Rhabdomyosarcoma is a type of cancer that can also affect the orbit. Enucleation of the eye can cause atrophy of the corresponding hemiface and decreased orbital growth. Case report We report a case of a female patient with a medical history of surgical enucleation of the right eyeball, who had received rhabdomyosarcoma radiation therapy in her youth. The patient presented with a depression in the right zygomatic region. We took a dermal-fat flap from the abdominal region, which had been previously treated. Results The surgical outcome, 48 hours, and much clearly 31 days after the surgery, revealed that the right zygomatic region had returned to its proper anatomical shape, although there were still signs of postoperative edema. Discussion Very damaged tissues, like those exposed to radiation therapy, are generally not suitable for grafting of adipose tissue. Conclusions In the described case, we achieved a technically and aesthetically satisfying result despite the patient's medical history involving several perplexities about the use of autologous dermal-fat tissues, because of prior radiation therapy exposure. The clinical case shows that even a region exposed to radiation therapy can be a valid receiving bed for dermal-fat grafting. PMID:23217096

2012-01-01

165

Effects of high energy simulated space radiation on polymeric second-surface mirrors. [thermal control coatings - performance tests  

NASA Technical Reports Server (NTRS)

A radiation effects experimental program was performed, in which second surface mirror type thermal control coatings were exposed to ultraviolet radiation, electrons, and protons simultaneously. Stability was assessed by making periodic spectral reflectance measurements in situ (and in air after testing for comparison). Solar absorption coefficients were derived by computer. Many of the exposed materials showed large amounts of degradation in reflectance absorptance, principally due to the electron exposure. A series of tests was conducted, leading to the identification of a modified second surface mirror that shows considerable improvement and promise for stability during thermal control applications in a charged particle space radiation environment.

Eogdall, L. B.; Cannaday, S. S.

1975-01-01

166

Modulation of graft architectures for enhancing hydrophobic interaction of biomolecules with thermoresponsive polymer-grafted surfaces.  

PubMed

This paper describes the effects of graft architecture of poly(N-isopropylacrylamide) (PIPAAm) brush surfaces on thermoresponsive aqueous wettability changes and the temperature-dependent hydrophobic interaction of steroids in silica capillaries (I.D.: 50 ?m). PIPAAm brushes were grafted onto glass substrates by surface-initiated atom transfer radical polymerization (ATRP) that is one of the living radical polymerization techniques. Increases in the graft density and chain length of PIPAAm brushes increased the hydration of polymer brushes, resulting in the increased hydrophilic properties of the surface below the transition temperature of PIPAAm at 32 °C. More hydrophobic surface properties were also observed on surfaces modified with the block copolymers of IPAAm and n-butyl methacrylate (BMA) than that with IPAAm homopolymer-grafted surfaces over the transition temperature. Using PBMA-b-PIPAAm-grafted silica capillaries, the baseline separation of steroids was successfully achieved by only changing temperature. The incorporation of hydrophobic PBMA chains in grafted PIPAAm enhanced the hydrophobic interaction with testosterone above the transition temperature. The surface modification of hydrophobicity-enhanced thermoresponsive polymers is a promising method for the preparation of thermoresponsive biointerfaces that can effectively modulated their biomolecule and cell adsorption with the wide dynamic range of hydrophilic/hydrophobic property change across the transition temperature. PMID:22143027

Idota, Naokazu; Kikuchi, Akihiko; Kobayashi, Jun; Sakai, Kiyotaka; Okano, Teruo

2012-11-01

167

Bone Graft Alternatives  

MedlinePLUS

... or during a surgical procedure such as spinal fusion. What Types of Bone Grafts are There? Bone ... bone grafts in spine surgery is during spinal fusion. The use of autogenous bone grafts for spinal ...

168

Coronary Artery Bypass Grafting  

MedlinePLUS

... from the NHLBI on Twitter. What Is Coronary Artery Bypass Grafting? Coronary artery bypass grafting (CABG) is ... bypass multiple coronary arteries during one surgery. Coronary Artery Bypass Grafting Figure A shows the location of ...

169

Preparation and characterization of Fe(III)-loaded iminodiacetic acid modified GMA grafted nonwoven fabric adsorbent for anion adsorption  

NASA Astrophysics Data System (ADS)

An Fe(III)-loaded chelating fabric with iminodiacetic acid (IDA) functional groups was prepared by radiation induced graft polymerization of an epoxy group containing monomer, glycidyl methacrylate, onto a nonwoven fabric made of polypropylene coated by polyethylene (PE/PP) and subsequent Fe(III) loading. Grafting conditions were optimized, and GMA grafted polymer was modified with iminodiacetic acid in isopropyl alcohol/water at 80 °C. In order to prepare the polymeric ligand exchanger (PLE) for the removal of phosphate, IDA fabrics were loaded with Fe(III) ions. Fe(III) loading capacity of IDA fabric was determined to be 2.83 mmol Fe(III)/g of polymer. For removal of phosphate anion, adsorption experiments were performed in batch mode at different pH (2-9) and phosphate concentrations. It was found that phosphate adsorption by the Fe(III)-loaded IDA fabric is maximum at pH 2.00. The effect of initial concentration of phosphate on the adsorption behaviour of Fe(III)-loaded IDA nonwoven fabric was determined at low phosphate concentrations (0.5-25 ppm) and at high phosphate concentrations (50-1000 ppm).

Kavakl?, P?nar Akka?; Kavakl?, Cengiz; Güven, Olgun

2014-01-01

170

Clinical factors increasing radiation doses to patients undergoing long-lasting procedures: Abdominal stent-graft implantation  

PubMed Central

Summary Background An important negative factor of EVAR is the radiation acquired during long-lasting procedures. The aim of the study was to document the radiation doses of EVAR and to discuss potential reasons for prolongation of radiological procedures. Material/Methods Dose-area product (DAP) (Gy cm2) and air kerma (AK) (Gy) obtained during EVAR from 92 patients were analyzed retrospectively in regards to body mass index (BMI), angulations of aneurysm neck, length of aneurysm neck and occurrence of tortuosity of iliac arteries. Results Total AK for fluoroscopy differed significantly between normal BMI (373 mGy) and BMI 25–29.9 (1125 mGy) or BMI >30 (1085 mGy). Iliac artery tortuosities >45° and short aneurysm necks caused higher doses of total AK (1097 mGy and 1228 mGy, respectively) than iliac artery tortuosities <45° and long aneurysm necks (605 mGy and 720 mGy, respectively). Conclusions The main factors contributing to a high radiation dose being acquired by patients during EVAR are: BMI >25, tortuosity of iliac arteries >45° and short aneurysm necks. PMID:22037751

Majewska, Natalia; Stanisic, Michal G.; Blaszak, Magdalena Aleksandra; Juszkat, Robert; Frankiewicz, Maciej; Krasinski, Zbigniew; Makalowski, Marcin; Majewski, Waclaw

2011-01-01

171

Preparation of acrylic grafted chitin for wound dressing application  

Microsoft Academic Search

Chitin grafted with poly(acrylic acid) (chitin–PAA) was prepared with the aim of obtaining a hydrogel characteristic for wound dressing application. The chitin–PAA films were synthesized at various acrylic acid feed contents to investigate its effect on water sorption ability. Acrylic acid (AA) was first linked to chitin, acting as the active grafting sites on the chain that was further polymerized

Siriporn Tanodekaew; Malinee Prasitsilp; Somporn Swasdison; Boonlom Thavornyutikarn; Thanawit Pothsree; Rujiporn Pateepasen

2004-01-01

172

Preparation of pH\\/temperature responsive polymer membrane by plasma polymerization and its riboflavin permeation  

Microsoft Academic Search

pH and temperature sensitive polymer membrane was prepared by grafting acrylic acid and N-isopropylacrylamide on the surface of porous polyamide membrane by plasma polymerization technique. Simultaneous plasma polymerization of two monomers yielded the membrane sensitive both to pH and temperature. Graft yield was lowered when acrylic acid content was over 10 wt% in monomer mixture. X-ray photoelectron spectra and Fourier

Young Moo Lee; Jin Kie Shim

1997-01-01

173

Polymeric Actuators.  

PubMed

Actuators are materials and devices that are able to change their shape in response to changes in environmental conditions and perform mechanical work on nano-, micro-, and macroscales. Among the huge variety of different actuators, polymer-based ones are highly attractive because of a number of properties such as sensitivity to a broad range of stimuli and good mechanical properties. The goal of this review is to provide a general picture of different mechanisms and working principles of polymeric actuators as well as to show a palette of their applications. PMID:25386998

Ionov, Leonid

2014-11-11

174

Structure–property relationships of irradiation grafted nano-inorganic particle filled polypropylene composites  

Microsoft Academic Search

An irradiation grafting method was applied for the modification of nanoparticles so that the latter can be added to polymeric materials for improving their mechanical performance, using existing compounding techniques. The following items are discussed in particular, in this paper: (a) chemical interaction between the grafting monomers and the nanoparticles during irradiation; (b) properties including modulus, yield strength, impact strength

Min Zhi Rong; Ming Qiu Zhang; Yong Xiang Zheng; Han Min Zeng; R Walter; K Friedrich

2001-01-01

175

Synthesis and Characterization of Poly(Acrylic Acid) and Poly(Glycidyl Methacrylate) Chitosan Graft Copolymers and Their Application to Cotton Fabric  

Microsoft Academic Search

Graft polymerization of acrylic acid (AA) and glycidyl methacrylate (GMA) onto chitosan was independently effected in a homogeneous aqueous phase under different conditions by using potassium bromate\\/thiourea as a combined redox system. The grafting reaction was monitored for carboxyl and epoxy groups in the case of AA and GMA, respectively. Also monitored were percentages of graft yield (GY%), homopolymer (HP%),

A. Hebeish; A. El-Shafei; M. El-Bisi

2005-01-01

176

Preparation of functionalized polystyrene latexes by radiation-induced miniemulsion polymerization using a Y-type polymerizable surfactant as sole stabilizers  

NASA Astrophysics Data System (ADS)

Functionalized polystyrene latexes were prepared by miniemulsion polymerization using a Y-type polymerizable surfactant bearing a carboxylic acid group as sole stabilizers. Kinetics analysis showed that there was no constant rate stage, which coincided with the kinetics mechanism of the typical miniemulsion polymerization. The latexes obtained were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. It was found that the latexes prepared by miniemulsion polymerization initiated by gamma-ray had more narrowly particle size distribution compared with by potassium persulfate. XPS and FTIR results indicated that the carboxyl group was present on the surface of the polymer particles.

Chen, Jun; Zhang, Zhicheng; Zhang, Qianfeng

2009-11-01

177

Electrostrictive Graft Elastomers  

NASA Technical Reports Server (NTRS)

An electrostrictive graft elastomer has a backbone molecule which is a non-crystallizable, flexible macromolecular chain and a grafted polymer forming polar graft moieties with backbone molecules. The polar graft moieties have been rotated by an applied electric field, e.g., into substantial polar alignment. The rotation is sustained until the electric field is removed. In another embodiment, a process for producing strain in an elastomer includes: (a) providing a graft elastomer having a backbone molecule which is a non-crystallizable, flexible macromolecular chain and a grafted polymer forming polar graft moieties with backbone molecules; and (b) applying an electric field to the graft elastomer to rotate the polar graft moieties, e.g., into substantial polar alignment.

Su, Ji (Inventor); Harrison, Joycelyn S. (Inventor); St.Clair, Terry L. (Inventor)

2003-01-01

178

Radiation-induced graft copolymerization of mixtures of styrene and acrylamide onto cellulose acetate. IV. Studies on some physical properties and structural characterization by means of scanning electron microscopy. [Gamma radiation  

SciTech Connect

Binary mixtures of monomers, e.g., styrene and acrylamide in 1:1 methanol:water solution, were grafted onto cellulose acetate film by taking recourse to preirradiation grafting procedure. The surface modification of the films due to grafting was examined by means of scanning electron microscopy. The mechanical properties, e.g., tensile strength elongation at break, and elasticity as well as water vapor permeability of the grafted films, were investigated. In the case of ungrafted films or when acrylamide was grafted to a low extent, the film surfaces were smooth and hence were not modified to any significant extent. But when acrylamide was grated appreciably, or when styrene was grafted singly or in binary mixture with acrylamide, the surfaces were found to be covered with fibrils. The pattern of the surface modification also changes with the increase of the extent of grafting. The observed properties of the grafted films were explained on the basis of the electron microscopic results. 18 references, 7 figures, 2 tables.

Bhattacharyya, S.N.; Maldas, D.

1984-05-01

179

Preparation of poly(ether ether ketone)-based polymer electrolytes for fuel cell membranes using grafting technique  

Microsoft Academic Search

Poly(ether ether ketone) (PEEK)-based polymer electrolyte membranes (PEMs) was successfully prepared by radiation grafting of a styrene monomer into PEEK films and the consequent selective sulfonation of the grafting chains in the film state. Using milder sulfonation, the sulfonation reactions proceeded at the grafted chains in preference to the phenylene rings of PEEK main chains; as a result, the grafted

Shin Hasegawa; Yasuyuki Suzuki; Yasunari Maekawa

2008-01-01

180

Hybrid molecular brushes with chitosan backbone: facile synthesis and surface grafting.  

PubMed

We developed a facile route toward amphiphilic hybrid molecular brushes (HMB) with chitosan backbone and concurrently grafted chains of poly(acrylamide) and polystyrene. The grafting occurs through amino groups of chitosan; no extra modification of chitosan is required. The kinetic and molecular weight characteristics of the primary molecular brush CHI-graft-PAAm are studied. The second step is grafting of PS by emulsion polymerization. The resulting HMB CHI-graft-PAAm-graft-PS form very stable emulsions. We attached the HMB on solid substrates using chitosan backbone by the "grafting to" approach. Thin films of the immobilized HMB of 3-11 nm thickness completely cover the surface. Being amphiphilic by nature, the immobilized HMB reveal the ability to adapt to the medium, which results in shifting of the hydrophobic/hydrophilic balance over a wide range. PMID:25438297

Hall-Edgefield, Desirae L; Shi, Tony; Nguyen, Kimmy; Sidorenko, Alexander

2014-12-24

181

Bone grafts in dentistry  

PubMed Central

Bone grafts are used as a filler and scaffold to facilitate bone formation and promote wound healing. These grafts are bioresorbable and have no antigen-antibody reaction. These bone grafts act as a mineral reservoir which induces new bone formation. PMID:23946565

Kumar, Prasanna; Vinitha, Belliappa; Fathima, Ghousia

2013-01-01

182

Polymeric Materials for Tissue Engineering of Arterial Substitutes  

PubMed Central

Cardiovascular disease is the leading cause of mortality in the United States. The limited availability of healthy autologous vessels for bypass grafting procedures has led to the fabrication of prosthetic vascular conduits. Synthetic polymeric materials, while providing the appropriate mechanical strength, lack the compliance and biocompatibility that bioresorbable and naturally occurring protein polymers offer. Vascular tissue engineering approaches have emerged in order to meet the challenges of designing a vascular graft with long-term patency. In vitro culture techniques that have been explored with vascular cell seeding of polymeric scaffolds and the use of bioactive polymers for in situ arterial regeneration have yielded promising results. This review describes the development of polymeric materials in various tissue engineering strategies for the improvement in the mechanical and biological performance of an arterial substitute. PMID:19426609

Ravi, Swathi; Qu, Zheng; Chaikof, Elliot L.

2009-01-01

183

Soft-Tissue Grafts (for Receding Gums)  

MedlinePLUS

... types of soft-tissue grafts: Free gingival grafts Connective-tissue grafts Pedicle grafts In a free gingival graft, ... need to have the gums enlarged. In a connective-tissue graft, a flap is cut in the roof ...

184

Fibrin as a matrix for grafting 2-hydroxyethyl methacrylate: preparation and characterization of the graft and its in vivo evaluation for wound healing.  

PubMed

In this work, fibrin was used as a substrate to graft 2-hydroxyethyl methacrylate (HEMA) by free radical polymerization using potassium persulfate and sodium metabisulfite as redox initiators. The extent of grafting the synthetic polymer on the biopolymer was studied under various experimental conditions, and the optimum factors for affording maximum grafting were standardized. The graft, fib-g-p[HEMA], was characterized by Fourier transform infrared, scanning electron microscopy, and X-ray diffraction studies. The graft exhibited a higher shelf life than native fibrin. The biocompatibility of the graft has been tested by in vivo studies and the results, in terms of collagen formation and wound size, proved its suitability for wound healing. PMID:12761832

Sathian, J; Sastry, T P; Suguna, L; Lakshminarayana, Y; Radhakrishnan, G

2003-06-15

185

Intraoperative grafts assessment.  

PubMed

Graft patency strongly influences early and late outcomes after coronary artery bypass grafting (CABG) surgery. The current standard of care in CABG surgery does not require intraoperative imaging. Because coronary angiography is rarely available in the operating room (OR), other techniques have been developed to assess graft integrity intraoperatively. The 2 most commonly used are the transit time flow measurement (TTFM) and the intraoperative fluorescence imaging (IFI). The TTFM is a quantitative volume flow technique, whereas the IFI is based on the fluorescent properties of indocyanine green. TTFM cannot define the degree of graft stenosis nor discriminate between the influence of the graft conduit and the coronary arteriolar bed on the mean graft flow. IFI provides a "semiquantitative" assessment of the graft patency with images that provide some details about the quality of coronary anastomoses. Both methods are valuable in identifying only at the extremes, that is, either patent or occluded grafts, and can confirm very good grafts; however, neither method is sensitive or specific enough in identifying more subtle abnormalities. These abnormal grafts most likely have poor long-term patency and are predestined to fail. The hybrid suite has the capability of serving both as a complete surgical OR and as a catheterization laboratory. It allows for routine completion angiogram following CABG surgery and identifies abnormal grafts, providing the opportunity to revise them with percutaneous coronary intervention or surgery before leaving the OR. PMID:19942118

Leacche, Marzia; Balaguer, Jorge M; Byrne, John G

2009-01-01

186

Grafting of 2 (2-hydroxy-5-vinylphenyl) 2H-benzotriazole onto polymers with aliphatic groups. Synthesis and polymerization of 2 (2-hydroxy-5-isopropenylphenyl) 2H-benzotriazole and a new synthesis of 2 (2-hydroxy-5-vinylphenyl) 2H-benzotriazole  

NASA Technical Reports Server (NTRS)

Successful grafting of 2(2-hydroxy-5-vinylphenyl)2H-benzotriazole onto saturated aliphatic C-H groups of polymers has been accomplished. When the grafting reaction was carried out in chlorobenzene at 150 C = 160 C with di-tertiarybutylperoxide as the grafting initiator, grafts as high as 20 percent - 30 percent at a grafting efficiency of 50 percent and 80 percent have readily been obtained. The grafting reaction was carried out in tubes sealed under high vacuum since trace amounts of oxygen cause complete inhibition of the grafting reaction by the phenolic monomer. On a variety of different polymers including atactic polypropylene, ethylene/vinyl acetate copolymer, poly(methyl methacrylate), poly(butyl acrylate), and polycarbonate were used.

Pradellok, W.; Nir, Z.; Vogl, O.

1981-01-01

187

One-step synthesis of amino-reserved chitosan- graft-polycaprolactone as a promising substance of biomaterial  

Microsoft Academic Search

One-step approach was developed to synthesize amino-reserved chitosan-graft-polycaprolactone (CS-g-PCL) by grafting ?-CL oligomers onto the hydroxyl groups of CS via ring-opening polymerization by using methanesulfonic acid as solvent and catalyst. The controllable grafting content of PCL within CS-g-PCL provided the possibility to manipulate the biodegradation rate, hydrophilicity, and hence the cytotoxicity of CS-g-PCL. As a result, the specimen synthesized from

Kongrong Duan; Honglin Chen; Jin Huang; Jiahui Yu; Shiyuan Liu; Daxin Wang; Yaping Li

2010-01-01

188

Surface-grafted polypeptides on flat substrates  

NASA Astrophysics Data System (ADS)

In this work, we improved the vapor deposition-polymerization (VDP) technique by re-designing a new vacuum chamber, and adding two heating plates to control the temperatures of the substrate and monomer evaporation. By optimizing the reaction parameters such as monomer amount, substrate temperature and reaction time, various polypeptides with sufficiently high molecular weight have been successfully grafted onto the solid substrates. The combination of VPD with photolithography has fabricated micro-patterned polypeptides, with geometry patternable in both lateral and vertical directions. Next, the conformations of the surface-grafted polypeptides were systematically examined. New ways have been found to switch their conformations between alpha-helix and beta-sheet, or between right-handed helix and left-handed helix. Two important ionic polypeptides, poly(L-glutamic acid) (PLGA) and poly(L-lysine) (PLL) were the focuses of this work. The conformational transitions of surface-grafted PLGA and PLL were successfully induced by pH, surfactants and ions. In addition, a surface-grafted PLGA-block-PLL copolypeptide was studied. Their unexpected pH-responsiveness was explained by the beta-sheet formation between the PLGA and PLL blocks. The orientation of the surface-grafted alpha-helical poly(gamma-benzyl L-glutamate) (PBLG) was greatly improved by a novel "solvent quenching" method, which involves treating the film sequentially with a good solvent and a poor solvent. The average tilt angle of the PBLG rods changed from 49° to 3° by applying this "quenching". Finally, a surface-grafted PLL film was used as the template to mimic the biosilicification. Silica was spontaneously synthesized from tetraethoxysilane inside the PLL film at room temperature and at neutral pH.

Wang, Yuli

189

Graft copolymers with immobilized peroxidase for organic synthesis  

NASA Astrophysics Data System (ADS)

The graft copolymer poly(propylene)-graft-poly(acrylic acid) (PP-G-AA) was prepared by radiation-induced graft copolymerization of acrylic acid onto polypropylene spheres and characterized by thermal analysis and scanning electron microscopy (SEM). Maximum percentage of grafting (70%) was obtained at a total dose of 12 kGy using 30% (w/w) of acrylic acid. The Michaelis constant, KM, and the maximum reaction velocity, VMax, were determined for the free horseradish peroxidase and for the immobilized horseradish peroxidase. The enzyme affinity for the substrate ( KM/ Vmax) remains quite good after immobilization. The sulfoxidation reaction of a ketosulfide was investigated with the immobilized peroxidase.

De Queiroz, Alvaro Antonio Alencar; Vargas, Reinaldo Romero; Higa, Olga Zazuco; Barrak, Élcio Rogério; Bechara, Etelvino J. H.; Wlasdislaw, Blanka; Marzorati, Liliana

1999-07-01

190

bacteria driven polymerization  

E-print Network

12/20/2007 1 Motion of bacteria driven by actin polymerization forces Michael C. DeSantis Physics.B. Alberts) Examples of other intracellular pathogens propelled by actoclampins (actin filament (+)-end by actin polymerization. Cell signaling and its influence by actin polymerization transitions

Wang, Yan Mei

191

Accelerated cell-sheet recovery from a surface successively grafted with polyacrylamide and poly(N-isopropylacrylamide).  

PubMed

A double polymeric nanolayer consisting of poly(N-isopropylacrylamide) (PIPAAm) and hydrophilic polyacrylamide (PAAm) was deposited on tissue culture polystyrene (TCPS) surfaces using electron beam irradiation to form a new temperature-responsive cell culture surface in which the basal hydrophilic PAAm component in the double polymeric layer promotes the hydration of the upper PIPAAm layer and induces rapid cell detachment compared to a conventional temperature-responsive cell culture surface, PIPAAm-grafted TCPS (PIPAAm-TCPS). Take-off angle-dependent X-ray photoelectron spectroscopy spectral analysis demonstrated that the grafted PIPAAm and PAAm components were located in the upper and basal regions of the double polymeric layer, respectively, suggesting that the double polymeric layer forms an inter-penetrating-network-like structure with PAAm at the basal portion of the PIPAAm grafted chains. The wettability of the temperature-responsive cell culture surfaces with the double polymeric layer tended to be more hydrophilic, with an increase in the basal PAAm graft density at a constant PIPAAm graft density. However, when the graft densities of the upper PIPAAm and basal PAAm were optimized, the resulting temperature-responsive cell culture surface with the double polymeric layer exhibited rapid cell detachment while maintaining cell adhesive character comparable to that of PIPAAm-TCPS. The cell adhesive character was altered from cell-adhesive to cell-repellent with increasing PAAm or PIPAAm graft density. The cell adhesive character of the temperature-responsive cell culture surfaces was relatively consistent with their contact angles. These results strongly suggest that the basal PAAm surface properties affect the degree of hydration and dehydration of the subsequently grafted PIPAAm. In addition, the roles of the hydrophilic component in accelerating cell detachment are further discussed in terms of the mobility of the grafted PIPAAm chains. Applications of this insight might be useful for designing temperature-responsive cell culture surfaces for achieving efficient cell culture and quick target cell detachment. PMID:24681372

Akiyama, Yoshikatsu; Kikuchi, Akihiko; Yamato, Masayuki; Okano, Teruo

2014-08-01

192

Hydroxyalkylation and polyether polyol grafting of graphene tailored for graphene/polyurethane nanocomposites.  

PubMed

Graphene functionalization by hydroxyalkylation and grafting with polyether polyols enables polyurethane (PU) nanocomposites formation by in situ polymerization with isocyanates combined with effective covalent interfacial coupling. Functionalized graphene (FG) hydroxylation is achieved either by alkylation, transesterification, or grafting of thermally reduced graphite oxide. In the presence of K2 CO3 as catalyst the reaction of FG-OH with ethylene carbonate at 180 °C affords hydroxyethylated FG, whereas transesterification with castor oil produces riconoleiate-modified FG polyols. In the "grafting-from" process, FG-alkoholate macro initiators initiate the graft polymerization of propylene oxide to produce hybrid FG polyols containing 38 and 59 wt% oligopropylene oxide. In the "grafting-to" process 3-ethyl-3-hydroxymethyl-oxetane is cationically polymerized onto FG-OH, producing novel hyperbranched FG-based polyether polyols. Whereas hydroxylation and grafting of FG greatly improve FG dispersion in organic solvents, polyols and even PU, as confirmed by transmission electron microscopy, matrix reinforcement of FG/PU is impaired by increasing alkyl chain length and polyol graft copolymer content. PMID:23836705

Appel, Anna-Katharina; Thomann, Ralf; Mülhaupt, Rolf

2013-08-01

193

Monolithic molecularly imprinted polymeric capillary columns for isolation of aflatoxins.  

PubMed

Monolithic molecularly imprinted polymers extraction columns have been prepared in fused-silica capillaries by UV or thermal polymerization in a two-step process. First, a poly-(trimethylolpropane trimethacrylate) (polyTRIM) core monolith was synthesized either by UV or thermal polymerization. Then it was grafted with the mixture of methacrylic acid (MAA) as a functional monomer, ethylene dimethacrylate (EDMA) as a cross-linking agent, 5,7-dimethoxycoumarin (DMC) as an aflatoxin-mimicking template, toluene as a porogen solvent and 2,2-azobis-(2-methylpropionitrile) (AIBN) as an initiator of the polymerization reaction. Different thermal condition of the photografting and different concentrations of the grafting mixture were tested during polymerization. The extraction capillary columns were evaluated in the terms of their hydrodynamic and chromatographic properties. Retention coefficients for aflatoxin B1 and DMC were used for assessment of the selectivity and imprinting factor. The obtained results indicate that the temperature of photografting and concentration of the grafting mixture are key parameters that determine the quality of the prepared MIPs. From the MIP columns characterized by the highest permeability the column of the highest imprinting factor was applied for isolation of aflatoxins B1, B2, G1 and G2 from the model aqueous sample followed by on-line chromatographic separation. The process was performed using a micro-MISPE-microLC-LIF system of a novel design, which allowed for detection of the eluates from the sample preparation part as well as from the chromatographic separation. PMID:25218633

Szumski, Micha?; Grzywi?ski, Damian; Prus, Wojciech; Buszewski, Bogus?aw

2014-10-17

194

Hybrid rigid/soft and biologic/synthetic materials: polymers grafted onto cellulose microcrystals.  

PubMed

Rigid nanoscale polymer rods were prepared by grafting preformed amine-terminated poly(styrene) and poly(tert-butyl acrylate) onto oxidized cellulose microcrystals. Low polydispersity polymers, grown using atom transfer radical polymerization, were characterized and purified prior to cellulose attachment. Oxidation of the cellulose microcrystal led to the formation of carboxylic acids on the surface of the microcrystals. Covalent attachment of the polymers onto the cellulose microcrystals was achieved via a carbodiimide-mediated amidation reaction. The length and diameter of the polymer-cellulose composites increased upon surface modification. Typically, polymer-cellulose composites are synthesized by a grafting-from method because it can be difficult to obtain sufficient graft density using a grafting-to preparation. However, the composites reported here comprised 60-64% grafted polymer by mass. This degree of grafting-to allowed the composite to form stable suspensions in organic solvents. PMID:21381766

Harrisson, Simon; Drisko, Glenna L; Malmström, Eva; Hult, Anders; Wooley, Karen L

2011-04-11

195

The graft polymers from different species of lignin and acrylic acid: synthesis and mechanism study.  

PubMed

The influence of lignin species on the grafting mechanism of lignosulfonate (from eucalyptus and pine, recorded as HLS and SLS, respectively) with acrylic acid (AA) was investigated. The graft polymers were confirmed by the absorption of carbonyl groups in the FTIR spectra. The decreasing phenolic group's content (Ph-OH) is not only due to its participation as grafting site but also to the negative effect of initiator. In the initial period (0-60 min), HLS and SLS both accelerate the polymerization of AA. Additionally, Ph-OH group's content is proportional to product yield (Y%), monomer conversion (C%) and grafting efficiency (GE%), strongly indicating that it acts as active center. Nevertheless, compared with HLS, Y% and C% in SLS grafting system are lower though it has higher Ph-OH group's content, which is due to the quinonoid structure formed by the self-conjugated of phenoxy radical in Guaiacyl unit. Finally, the lignosulfonate grafting mechanism was proposed. PMID:24076194

Ye, De zhan; Jiang, Li; Ma, Chao; Zhang, Ming-hua; Zhang, Xi

2014-02-01

196

The preparation of graft copolymers of cellulose and cellulose derivatives using ATRP under homogeneous reaction conditions.  

PubMed

In this comprehensive review, we report on the preparation of graft-copolymers of cellulose and cellulose derivatives using atom transfer radical polymerization (ATRP) under homogeneous conditions. The review is divided into four sections according to the cellulosic material that is graft-copolymerised; (i) cellulose, (ii) ethyl cellulose, (iii) hydroxypropyl cellulose and (iv) other cellulose derivatives. In each section, the grafted synthetic polymers are described as well as the methods used for ATRP macro-initiator formation and graft-copolymerisation. The physical properties of the graft-copolymers including their self-assembly in solution into nanostructures and their stimuli responsive behaviour are described. Potential applications of the self-assembled graft copolymers in areas such as nanocontainers for drug delivery are outlined. PMID:25016958

Joubert, Fanny; Musa, Osama M; Hodgson, David R W; Cameron, Neil R

2014-10-21

197

A Versatile Star PEG Grafting Method for the Generation of Nonfouling and Nonthrombogenic Surfaces  

PubMed Central

Polyethylene glycol (PEG) grafting has a great potential to create nonfouling and nonthrombogenic surfaces, but present techniques lack versatility and stability. The present work aimed to develop a versatile PEG grafting method applicable to most biomaterial surfaces, by taking advantage of novel primary amine-rich plasma-polymerized coatings. Star-shaped PEG covalent binding was studied using static contact angle, X-ray photoelectron spectroscopy (XPS), and quartz crystal microbalance with dissipation monitoring (QCM-D). Fluorescence and QCM-D both confirmed strong reduction of protein adsorption when compared to plasma-polymerized coatings and pristine poly(ethyleneterephthalate) (PET). Moreover, almost no platelet adhesion was observed after 15?min perfusion in whole blood. Altogether, our results suggest that primary amine-rich plasma-polymerized coatings offer a promising stable and versatile method for PEG grafting in order to create nonfouling and nonthrombogenic surfaces and micropatterns. PMID:23509823

Thalla, Pradeep Kumar; Contreras-García, Angel; Fadlallah, Hicham; Barrette, Jérémie; De Crescenzo, Gregory; Merhi, Yahye; Lerouge, Sophie

2013-01-01

198

Controlled atom transfer radical polymerization of MMA onto the surface of high-density functionalized graphene oxide  

PubMed Central

We report on the grafting of poly(methyl methacrylate) (PMMA) onto the surface of high-density functionalized graphene oxides (GO) through controlled radical polymerization (CRP). To increase the density of surface grafting, GO was first diazotized (DGO), followed by esterification with 2-bromoisobutyryl bromide, which resulted in an atom transfer radical polymerization (ATRP) initiator-functionalized DGO-Br. The functionalized DGO-Br was characterized by X-ray photoelectron spectroscopy (XPS), Raman, and XRD patterns. PMMA chains were then grafted onto the DGO-Br surface through a ‘grafting from’ technique using ATRP. Gel permeation chromatography (GPC) results revealed that polymerization of methyl methacrylate (MMA) follows CRP. Thermal studies show that the resulting graphene-PMMA nanocomposites have higher thermal stability and glass transition temperatures (Tg) than those of pristine PMMA. PMID:25114639

2014-01-01

199

Free radical grafting kinetics of acrylamide onto a blend of starch/chitosan/alginate.  

PubMed

Grafting of monomer onto polymer backbone is one of the effective and accessible methods for the chemical modification of polysaccharides. Grafting of acrylamide (AAm) onto polysaccharides blend (PsB) composed of starch, chitosan and alginate has been carried out using potassium persulfate (KPS) as an initiator. The kinetics of the grafting polymerization also has been studied. The grafting parameters have been evaluated by changing the initial concentrations of AAm from 8 to 16 g, PsB from 6 to 14 g and KPS from 0.2 to 1 g. Evidence of grafting has been obtained from FTIR, XRD and TGA. The kinetics of the grafting polymerization also has been studied. The grafting rate equation of the produced hydrogel (PsB-g-AAm) hydrogel has been expressed by: Rg=k[AAm] [PsB](0.5) [KPS](0.5). The grafting rate is a first order dependence to [AAm] initial concentration and square root to [PsB] and [KPS] initial concentrations in the used concentrations range. PMID:23987368

Sorour, Mohamed; El-Sayed, Marwa; El Moneem, Nabil Abd; Talaat, Hala; Shaalan, Hayam; El Marsafy, Sahar

2013-10-15

200

Design of modified plastic surfaces for antimicrobial applications: Impact of ionizing radiation on the physical and mechanical properties of polypropylene  

NASA Astrophysics Data System (ADS)

Surface modification of polypropylene (PP) sheets was carried out by radiation induced graft polymerization of hydrophilic functional molecules such as N,N-dimethylacrylamide (DMA) and [2-methacryloyloxy)ethyl] trimethylammonium chloride, which is a quaternary ammonium salt (QAS). Polypropylene sheets were activated prior to the grafting reaction by using electron beam radiation. The changes in morphology, crystallinity and tensile parameters like deformation and stress at yield and deformation at break of PP after irradiation were investigated. The results showed that a minor crystalline reorganization takes place during the irradiation of PP at 100 kGy. The grafting has been observed to be strongly dependent on the monomer dilution in the reaction medium. After grafting of QAS (40%) and DMA (20%) it was possible to develop highly hydrophilic surfaces (water contact angle comprised between 30 and 41°). The surfaces of virgin, irradiated and grafted PP were studied using polarized optical microscopy (POM) and scanning electron microscopy (SEM). Spherical particles (i.e. polystyrene or silica beads) adhering to the modified samples were studied according to the surface parameters. Adhesion tests confirmed the strong influence of substrate type (mainly hydrophilicity and roughness) and to a lesser extent underlined the role of electrostatic interactions for the design of plastic surfaces for antimicrobial applications.

Riquet, Anne-Marie; Delattre, Jennifer; Vitrac, Olivier; Guinault, Alain

2013-10-01

201

ATRP of Amphiphilic Graft Copolymers Based on PVDF and Their Use as Membrane Additives  

Microsoft Academic Search

The direct preparation of amphiphilic graft copolymers from commercial poly(vinylidene fluoride) (PVDF) using atom transfer radical polymerization (ATRP) is demonstrated. Here, direct initiation of the secondary fluorinated site of PVDF facilitates grafting of the hydrophilic comonomer. Amphiphilic comb copolymer derivatives of PVDF having poly(methacrylic acid) side chains (PVDF-g- PMAA) and poly(oxyethylene methacrylate) side chains (PVDF-g-POEM) are prepared using this method.

J. F. Hester; P. Banerjee; Y.-Y. Won; A. Akthakul; M. H. Acar; A. M. Mayes

2002-01-01

202

Radiation-induced solid-state polymerization in an acrylamide-water system: The effect of phase transformations of metastable high-pressure ice VIII  

SciTech Connect

A drastic suppression of the chain post polymerization process in the quenched high-pressure phase of an acrylamide-water eutectic mixture was observed upon warming of the samples irradiated with {gamma}-rays at 77 K. This effect is explained by dispersion of the samples in the temperature region of the transition of the quenched high-pressure phase into the equilibrium phase ({approximately}150K). The size of the resulting microcrystals of monomer was estimated to be approximately 0.1 {mu}m.

Kiryukhin, D.P.; Barkalov, I.M. [Institute of Chemical Physics in Chernogolovka, Chernogolovka (Russian Federation); Barkalov, O.I. [Institute of Solid-State Physics, Chernogolovka (Russian Federation)

1995-07-01

203

Thermo-responsive polymer brush-grafted porous polystyrene beads for all-aqueous chromatography.  

PubMed

Poly(N-isopropylacrylamide) (PIPAAm) brush-grafted porous polystyrene beads with variable grafted polymer densities were prepared using surface-initiated atom transfer radical polymerization (ATRP) for applications in thermo-responsive chromatography. Utilization of these grafted beads as a stationary phase in aqueous chromatographic analysis of insulin provides a graft density-dependent analyte retention behavior. The separations calibration curve on PIPAAm-grafted polystyrene was obtained using pullulan standards and exhibited inflection points attributed to analyte diffusion into bead pores and partitioning into grafted PIPAAm brush surfaces. Presence of these inflection points supports a separation mechanism where insulin penetrates pores in polystyrene beads and hydrophobically interacts with PIPAAm brushes grafted within the pores. Control of PIPAAm brush graft density on polystyrene facilitates effective aqueous phase separation of peptides based on thermally modulated hydrophobic interactions with grafted PIPAAm within stationary phase pores. These results indicated that PIPAAm brush-grafted porous polystyrene beads prepared by surface-initiated ATRP was effective stationary phase of thermo-responsive chromatography for aqueous phase peptide separations. PMID:20015506

Mizutani, Aya; Nagase, Kenichi; Kikuchi, Akihiko; Kanazawa, Hideko; Akiyama, Yoshikatsu; Kobayashi, Jun; Annaka, Masahiko; Okano, Teruo

2010-01-22

204

Functionalization of multiwalled carbon nanotubes with polystyrene under atom transfer radical polymerization conditions  

Microsoft Academic Search

Linear Polystyrene (PS) was grafted onto the convex surfaces of multiwalled carbon nanotubes (MWCNTs). Bromine-terminated polystyrene synthesized by atom transfer radical polymerization (ATRP) was directly reacted with MWCNTs under ATRP conditions using CuBr\\/2,2?-bipyridine as catalyst. The PS-grafted MWCNT samples were characterized by scanning electron microscopy, transmission electron microscopy, FT-IR spectra, Raman spectra, 1H NMR, UV–vis spectra, thermal gravimetric analyses, and

Hui-Xia Wu; Rui Tong; Xue-Qiong Qiu; Hai-Feng Yang; Yang-Hui Lin; Rui-Fang Cai; Shi-Xiong Qian

2007-01-01

205

Bioactive Polymer Grafting onto Titanium Alloy Surfaces for Improved Osteointegration  

PubMed Central

Bioactive polymers bearing sulfonate (styrene sodium sulfonate, NaSS) and carboxylate (methylacrylic acid, MA) groups were grafted onto Ti6Al4V alloy surfaces by a two-step procedure. The Ti alloy surfaces were first chemically oxidized in a piranha solution and then directly subjected to radical polymerization at 70°C in absence of oxygen. The grafted surfaces were characterized by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and the Toluidin blue colorimetric method. Toluidin blue results showed 1 to 5 ?g/cm2 of polymer was grafted onto the oxidized Ti surfaces. Grafting resulted in a decrease in the XPS Ti and O signals from the underlying Ti substrate and a corresponding increase in the XPS C and S signals from the polymer layer. The ToF-SIMS intensities of the S? and SO? ions correlated linearly with the XPS atomic percent S concentrations and the ToF-SIMS intensity of the TiO3H2? ion correlated linearly with the XPS atomic percent Ti concentration. Thus, the ToF-SIMS S?, SO? and TiO3H2? intensities can be used to quantify composition and amount of grafted polymer. ToF-SIMS also detected ions that were more characteristic of the polymer molecular structure (C6H4SO3? and C8H7SO3? from NaSS, C4H5O2? from MA), but the intensity of these peaks depended on the polymer thickness and composition. An in vitro cell culture test was carried out with human osteoblast-like cells to assess the influence of the grafted polymers on cell response. Cell adhesion after 30 min of incubation showed significant differences between the grafted and un-grafted surfaces. The NaSS grafted surfaces showed the highest degree of cell adhesion while the MA-NaSS grafted surfaces showed the lowest degree of cell adhesion. After 4 weeks in vivo in rabbit femoral bones bone was observed to be in direct contact with all implants. The percent of mineralized tissue around the implants was similar for NaSS grafted and non-grafted implants (59 and 57%). The MA-NaSS grafted implant exhibited a lower amount of mineralized tissue (47%). PMID:19733698

Michiardi, Alexandra; Hélary, Gérard; Nguyen, Phuong-Cac Thi; Gamble, Lara J.; Anagnostou, Fani; Castner, David G.; Migonney, Véronique

2013-01-01

206

Bone graft substitutes.  

PubMed

Replacement of missing bone stock is a reconstructive challenge to upper extremity surgeons and decision-making with regards to available choices remains difficult. Preference is often given to autograft in the form of cancellous, cortical, or corticocancellous grafts from donor sites. However, the available volume from such donor sites is limited and fraught with potential complications. Advances in surgical management and medical research have produced a wide array of potential substances that can be used for bone graft substitute. Considerations in selecting bone grafts and substitutes include characteristic capabilities, availability, patient morbidity, immunogenicity, potential disease transmission, and cost variability. PMID:23101596

Bhatt, Reena A; Rozental, Tamara D

2012-11-01

207

Development of functionalized cellulosic biopolymers by graft copolymerization.  

PubMed

Natural lignocellulosic polymers are one of the most promising biodegradable, non-toxic and eco-friendly polymeric materials which have been used to develop various products for number of applications especially in green composites. However, these cellulosic materials have certain drawbacks, like sensitivity to water and moisture, and need to be modified. So in this article, a treatment of lignocellulose biopolymers with suitable acrylate monomer was investigated. The influence of different reaction parameters on efficiency (grafting) was investigated. SEM, TGA and Fourier transform infrared spectroscopy (FT-IR) were used to study the graft copolymerization between the monomer and hydroxyl groups of lignocellulosic biopolymers. This article also discusses swelling, and chemical resistance properties of the both the grafted/ungrafted cellulosic biopolymer and their potential candidature for green composite applications. PMID:23994197

Thakur, Vijay Kumar; Thakur, Manju Kumari; Gupta, Raju Kumar

2013-11-01

208

Phase Behavior and Significantly Enhanced Toughness in Polylactide Graft Copolymers  

NASA Astrophysics Data System (ADS)

Polylactide (PLA), a biodegradable polyester derived from plant sugars, is commercially available and used in a variety of applications ranging from serviceware to resorbable sutures. One limitation to diversifying the applications of the material is its inherent brittleness. Graft copolymers containing PLA arms and a rubbery aliphatic polymer backbone were synthesized by a combination of ring-opening metathesis and ring-opening transesterification polymerizations. The high degree of incompatibility between the arms and backbone resulted in microphase separation of the graft copolymer at increasingly low fractions of the backbone polymer, as evidenced by small-angle x-ray scattering. In graft copolymers with a rubbery content of only 5 wt percent, the tensile strain at break was observed to be as high as twenty times that of neat PLA. Studies are underway to provide insight into the critical polymer molecular parameters for enhanced toughness and the deformation mechanisms.

Robertson, Megan; Theryo, Grayce; Jing, Feng; Hillmyer, Marc

2011-03-01

209

Step-Growth Polymerization.  

ERIC Educational Resources Information Center

Following a comparison of chain-growth and step-growth polymerization, focuses on the latter process by describing requirements for high molecular weight, step-growth polymerization kinetics, synthesis and molecular weight distribution of some linear step-growth polymers, and three-dimensional network step-growth polymers. (JN)

Stille, J. K.

1981-01-01

210

Making Polymeric Microspheres  

NASA Technical Reports Server (NTRS)

Combination of advanced techniques yields uniform particles for biomedical applications. Process combines ink-jet and irradiation/freeze-polymerization techniques to make polymeric microspheres of uniform size in diameters from 100 to 400 micrometer. Microspheres used in chromatography, cell sorting, cell labeling, and manufacture of pharmaceutical materials.

Rhim, Won-Kyu; Hyson, Michael T.; Chung, Sang-Kun; Colvin, Michael S.; Chang, Manchium

1989-01-01

211

Thermodynamics of Polymerization. I  

Microsoft Academic Search

I. THE CHILING TEMPERATURE CONCEPT A. Thermodynamic Approach The Gibbs free energy of a system at temperature T is defined as were H is the enthalpy and S the entropy of the system. The free energy change for any polymerization will be, therefore, When the polymer has a lower free energy than the initial monomer, a polymerization can occur spontaneously,

Hideo Sawada

1969-01-01

212

Vein graft failure.  

PubMed

After the creation of an autogenous lower extremity bypass graft, the vein must undergo a series of dynamic structural changes to stabilize the arterial hemodynamic forces. These changes, which are commonly referred to as remodeling, include an inflammatory response, the development of a neointima, matrix turnover, and cellular proliferation and apoptosis. The sum total of these processes results in dramatic alterations in the physical and biomechanical attributes of the arterialized vein. The most clinically obvious and easily measured of these is lumen remodeling of the graft. However, although somewhat less precise, wall thickness, matrix composition, and endothelial changes can be measured in vivo within the healing vein graft. Recent translational work has demonstrated the clinical relevance of remodeling as it relates to vein graft patency and the systemic factors influencing it. By correlating histologic and molecular changes in the vein, insights into potential therapeutic strategies to prevent bypass failure and areas for future investigation are explored. PMID:24095042

Owens, Christopher D; Gasper, Warren J; Rahman, Amreen S; Conte, Michael S

2015-01-01

213

Grafting in rhinoplasty.  

PubMed

Advances in grafting techniques have provided the basis for a paradigm shift in rhinoplasty in which purely reductive techniques have been largely supplanted by structurally sound framework surgery. Proficiency with autologous cartilage grafting allows the rhinoplasty surgeon to achieve superior nasal definition and durable aesthetic outcomes by building a stable nasal framework that resists the contractile forces of healing responsible for delayed nasal airway compromise and aesthetic distortion. Cartilage grafts may be used to reposition, augment, or reconstitute nasal structure after cartilaginous resection and recontouring. The authors present various grafting techniques that are reliably used to sculpt the nasal framework in rhinoplasty, with emphasis on the relevant anatomy, nomenclature, and clinical indications for each approach. Judicious use of these methods results in predictable rhinoplasty outcomes with enhanced aesthetics and function. PMID:19181282

Brenner, Michael J; Hilger, Peter A

2009-02-01

214

Flame retardant brominated styrene-based polymers. VI. Synthesis and characterization of dibromostyrene graft latices  

SciTech Connect

Nine dibromostyrene-grafted commercial lattices were prepared in 8 oz bottles by an emulsion polymerization technique. Proper selection of lattices used in conjunction with the dibromostyrene monomer enables production of flame retardant latex products useful in a wide range of coating applications. The prime factor to be considered in the choice of a latex or a latex mixture to be grafted is the glass transition temperature(s) of the polymer(s) in the final latex desired. Lattices chosen for grafting are commercial lattices, such as Rhoplex HA-24 and HA-8, Hystretch V-29, Airflex 465, 4500, 4514 and 4530, Pliolite SBR latex and polybutadiene latex. The graft latex was characterized in terms of glass transition temperature, solids content, bromine content, grafted dibromostyrene and flame retardancy.

Favstritsky, N.A.; Wang, J.L. [Great Lakes Chemical Corp., West Lafayette, IN (United States)

1995-12-01

215

Graft copolymerization of ethyl acrylate onto tamarind kernel powder, and evaluation of its biodegradability.  

PubMed

In the present study, tamarind kernel powder and ethyl acrylate were reacted by free radical polymerization to synthesize a grafted copolymer soluble in water. The grafted copolymer was analyzed by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR); FTIR showed a shift of the vibration of R-CO-OR' from 1258 cm(-1) to 1253 cm(-1). This shift appeared because of the grafting copolymerization. Films were prepared to study the mechanical properties and the biodegradation of this material. The mechanical properties of the grafted copolymer were found to lie between those of the parent polymers, suitable for disposable products. The new grafted copolymer manifested a steady process of biodegradation under incubation with the bacterial strain Alicycliphilus sp. BQ1; this was proved by scanning electron microscopy (SEM) and near infrared spectroscopy (NIR). PMID:25498603

del Real, Alicia; Wallander, Daniela; Maciel, Alfredo; Cedillo, Gerardo; Loza, Herminia

2015-03-01

216

[History of skin graft].  

PubMed

Skin graft is the most common and simple procedure to cover superficial defect. Skin of variable thickness and size is completely detached from its origin (donor site) to cover a defect (recipient site). This simple procedure is the result of a long and eventful technical and theoretical evolvement. The aim of this article is to re-trace the history of skin grafting, from its discovery until today. PMID:19939539

Boudana, D; Wolber, A; Coeugniet, E; Martinot-Duquennoy, V; Pellerin, P

2010-08-01

217

Treatment of oil in water emulsions by ceramic-supported polymeric membranes  

SciTech Connect

A novel membrane was developed by growing polymer chains from the surface of a porous ceramic support, resulting in a composite membrane which combines the mechanical properties of the inorganic membrane with the selective interactions of the polymer. The configuration of the grafted polymer brush layer is determined by solvent-polymer interactions, with a hydrophilic polymer being stretched away from the surface by aqueous solutions and collapsed against the surface by organic solvents. This behavior of the grafted chains provides Ceramic-Supported Polymeric (CSP) membranes with unique properties for certain water treatment applications. One application envisioned for these CSP membranes, in which the selectivity is influenced by interactions between the solvent and the grafted polymer, is the cross-flow filtration of an oil-in-water emulsion. In this case, a hydrophilic grafted Polyvinylpyrrolidone (PVP) brush layer expanded into the pore volume due to the affinity of the polymer for water. These extended grafted chains preferentially allow the passage of water over oil, producing a permeate stream with a lower total organic carbon content compared to an unmodified membrane. Another advantage of the CSP membrane is in reducing permeate flux decline believed to be caused by the adsorption of oil onto the membrane surface. For the PVP-modified CSP membrane, the grafted polymer alters the membrane surface character from hydrophobic to hydrophilic, reducing the tendency for oil adsorption. This phenomenon was demonstrated by comparison of permeate flow rate behavior for both unmodified and graft polymerized (CSP) membranes.

Castro, R.P.; Cohen, Y.; Monbouquette, H.G. [Univ. of California, Los Angeles, CA (United States). Dept. of Chemical Engineering

1994-12-31

218

Structure of polymer layers grafted to nanoparticles in silica-polystyrene nanocomposites  

E-print Network

The structural features of polystyrene brushes grafted on spherical silica nanoparticles immersed in polystyrene are investigated by means of a Monte Carlo methodology based on polymer mean field theory. The nanoparticle radii (either 8 nm or 13 nm) are held constant, while the grafting density and the lengths of grafted and matrix chains are varied systematically in a series of simulations. The primary objective of this work is to simulate realistic nanocomposite systems of specific chemistry at experimentally accessible length scales and study the structure and scaling of the grafted brush. The profiles of polymer density around the particles are examined; based on them, the brush thickness of grafted chains is estimated and its scaling behavior is compared against theoretical models and experimental findings. Then, neutron scattering spectra are predicted both from single grafted chains and from the entire grafted corona. It is found that increasing both the grafting density and the grafted chain molar mass drastically alters the brush dimensions, affecting the wetting behavior of the polymeric brush. On the contrary, especially for particles dispersed in high molecular weight matrix, variation of the matrix chain length causes an almost imperceptible change of the density around the particle surface.

Georgios G. Vogiatzis; Doros N. Theodorou

2014-01-16

219

Multiphase Polymeric Materials  

NSDL National Science Digital Library

Developed by a group of PhD students at the University of Southern Mississippi, the Multiphase Polymeric Materials Website presents both general information about composites and current research on multiphase polymeric materials, including information about blends, coatings, and nanocomposites. As the newest addition to Macrogalleria (described in the March 31, 1999 Scout Report for Science & Engineering), the Multiphase Polymeric Materials Website includes information on Composites in General, Composites, Characterization and Analysis, and Application. Most useful to researchers, the Application section introduces the relationship between polymer composites and component level electronics with examples such as PCB Construction, Encapsulation of Integrated Circuits, and Non-Conductive Adhesives.

220

Nanostructural surface engineering of grafted polymers on inorganic oxide substrates for membrane separations  

NASA Astrophysics Data System (ADS)

Nanostructural engineering of inorganic substrates by free radical graft polymerization was studied with the goal of developing new membrane materials for pervaporation. Graft polymerization consisted of modification of surface hydroxyls with vinyl trimethoxysilane, followed by solution graft polymerization reaction using either vinyl acetate (VAc) or vinyl pyrrolidone (VP). The topology of the modified surfaces was studied by atomic force microscopy (AFM) on both atomically smooth silicon wafer substrates and microporous inorganic membrane supports in order to deduce the effects of modification on the nanostructural properties of the membrane. While unmodified wafers showed a root-mean-square (RMS) surface roughness of 0.21 +/- 0.03 nm, roughness increased to 3.15 +/- 0.23 nm upon silylation. Under poor solvent conditions (i.e., air), surfaces modified with higher poly(vinyl acetate) (PVAc) or poly(vinyl pyrrolidone) (PVP) polymer graft yields displayed lateral inhomogeneities in the polymer layer. Although RMS surface roughness was nearly identical (0.81--0.85 nm) for PVAc-modified surfaces grafted at different monomer concentrations, the skewness of the height distribution decreased from 2.22 to 0.78 as polymer graft yield increased from 0.8 to 3.5 mg/m2. The polymer-modified surfaces were used to create inorganic pervaporation membranes consisting of a single macromolecular separation layer formed by graft polymerization. PVAc grafted silica membranes (500A native pore size) were found selective for MTBE in the separation of 0.1--1% (v/v) MTBE from water, achieving MTBE enrichment factors as high as 371 at a permeate flux of 0.38 l/m2 hr and a Reynolds number of 6390; however, these membranes could not separate anhydrous organic mixtures. Pervaporative separation of methanol/MTBE mixtures was possible with PVAc and PVP-modified alumina supports of 50A native pore size, where the separation layer consisted of grafted polymer chains with estimated radius of gyration 4.5--6.8 times larger than the membrane pore radius. Methanol separation factors for the PVP and PVAc-grafted alumina pervaporation membranes reached values of 26 and 100 (respectively) at total permeate fluxes of 0.055--1.26 kg/m 2 hr and 0.55--6.19 kg/m2 hr. The present study demonstrated that selective pervaporation membranes for separation of both organic/organic and organic/aqueous mixtures can be effectively designed by careful selection of the surface-grafted polymer chain density and the ratio of the polymer chain size to the native support pore size.

Yoshida, Wayne Hiroshi

221

An in Vitro Study of Heparin-Immobilized Poly(Ethylene-Graft-Vinylacetate) and Poly(Ethylene-Graft-Vinylpyridine)  

Microsoft Academic Search

Polyethylene (PE) was modified by radiation-induced grafting of vinyl acetate (VAc) and vinyl pyridine (VP), followed by heparinization of the surface. The unmodified, the grafted, and the heparin-immobilized samples were studied with X-ray photoelectron spectroscopy. The heparinized samples were also studied by Laser Scanning Confocal Microscopy and by the toluidine blue method. The biological activity of heparin against thrombin formation

Eija Säilynoja; Mika Koskinen; Jukka Salonen; Anders Södergård

2001-01-01

222

Poly(methyl methacrylate) grafted imogolite nanotubes prepared through surface-initiated ARGET ATRP.  

PubMed

Poly(methyl methacrylate) grafted imogolite clay nanotubes were fabricated via activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) by designing a water-soluble amphiphilic ATRP initiator that can adsorb onto imogolite surface in an aqueous solution. PMID:21487609

Ma, Wei; Otsuka, Hideyuki; Takahara, Atsushi

2011-05-28

223

Impact of reaction conditions on architecture and rheological properties of starch graft polyacrylamide polymers  

Technology Transfer Automated Retrieval System (TEKTRAN)

We carried out experiments examining the impact that solvent selection and reaction conditions have on the radical initiated graft polymerization reaction of acrylamide onto starch. We have also evaluated the rheological properties the starch graftpolyacrylamide product when a gel is formed in water...

224

Synthesis and characterization of a novel amphiphilic chitosan–polylactide graft copolymer  

Microsoft Academic Search

Water soluble chitosan (CS) derivatives containing polylactide unit were synthesized by reacting dl-lactide (DLLA) with chitosan in dimethyl sulfoxide solution in the presence of triethylamine. The chemical structure and physical properties of chitosan derivatives were characterized by FTIR, 1HNMR, TGA and XRD. Formation and characteristics of polymeric micelles of graft copolymers were studied by fluorescence spectroscopy and dynamic light scattering

Yan Wu; Yongli Zheng; Wuli Yang; Changchun Wang; Jianhua Hu; Shoukuan Fu

2005-01-01

225

Preparation and characterization of poly(acrylic acid)-hydroxyethyl cellulose graft copolymer.  

PubMed

Poly(acrylic acid) hydroxyethyl cellulose [poly(AA)-HEC] graft copolymer was prepared by polymerizing acrylic acid (AA) with hydroxyethyl cellulose (HEC) using potassium bromate/thiourea dioxide (KBrO(3)/TUD) as redox initiation system. The polymerization reaction was carried out under a variety of conditions including concentrations of AA, KBrO(3) and TUD, material to liquor ratio and polymerization temperature. The polymerization reaction was monitored by withdrawing samples from the reaction medium and measuring the total conversion. The rheological properties of the poly(AA)-HEC graft copolymer were investigated. The total conversion and rheological properties of the graft copolymer depended on the ratio of KBrO(3) to TUD and on acrylic acid concentration as well as temperature and material to liquor ratio. Optimum conditions of the graft copolymer preparation were 30 mmol KBrO(3) and 30 mmol TUD/100g HEC, 100% AA (based on weight of HEC), duration 2h at temperature 50 °C using a material to liquor ratio of 1:10. PMID:22840022

Abdel-Halim, E S

2012-10-01

226

Who Needs Coronary Artery Bypass Grafting?  

MedlinePLUS

... from the NHLBI on Twitter. Who Needs Coronary Artery Bypass Grafting? Coronary artery bypass grafting (CABG) is ... Artery Bypass Grafting, visit www.clinicaltrials.gov . Coronary Artery Bypass Grafting in the News November 18, 2014 ...

227

Orthopaedic applications of bone graft & graft substitutes: a review.  

PubMed

Treatment of delayed union, malunion, and nonunion is a challenge to the orthopaedic surgeons in veterinary and human fields. Apart from restoration of alignment and stable fixation, in many cases adjunctive measures such as bone-grafting or use of bone-graft substitutes are of paramount importance. Bone-graft materials usually have one or more components: an osteoconductive matrix, which acts as scaffold to new bone growth; osteoinductive proteins, which support mitogenesis of undifferentiated cells; and osteogenic cells, which are capable of forming bone in the appropriate environment. Autologous bone remains the "gold standard" for stimulating bone repair and regeneration, but its availability may be limited and the procedure to harvest the material is associated with complications. Bone-graft substitutes can either substitute autologous bone graft or expand an existing amount of autologous bone graft. We review the currently available bone graft and graft substitutes for the novel therapeutic approaches in clinical setting of orthopaedic surgery. PMID:20693585

Nandi, S K; Roy, S; Mukherjee, P; Kundu, B; De, D K; Basu, D

2010-07-01

228

PREFACE: IUMRS-ICA 2008 Symposium, Sessions 'X. Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science' and 'Y. Frontier of Polymeric Nano-Soft-Materials - Precision Polymer Synthesis, Self-assembling and Their Functionalization'  

NASA Astrophysics Data System (ADS)

Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science (Symposium X of IUMRS-ICA2008) Toshiji Kanaya, Kohji Tashiro, Kazuo Sakura Keiji Tanaka, Sono Sasaki, Naoya Torikai, Moonhor Ree, Kookheon Char, Charles C Han, Atsushi Takahara This volume contains peer-reviewed invited and contributed papers that were presented in Symposium X 'Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science' at the IUMRS International Conference in Asia 2008 (IUMRS-ICA 2008), which was held on 9-13 December 2008, at Nagoya Congress Center, Nagoya, Japan. Structure analyses of soft materials based on synchrotron radiation (SR) and neutron beam have been developed steadily. Small-angle scattering and wide-angle diffraction techniques clarified the higher-order structure as well as time dependence of structure development such as crystallization and microphase-separation. On the other hand, reflectivity, grazing-incidence scattering and diffraction techniques revealed the surface and interface structural features of soft materials. From the viewpoint of strong interests on the development of SR and neutron beam techniques for soft materials, the objective of this symposium is to provide an interdisciplinary forum for the discussion of recent advances in research, development, and applications of SR and neutron beams to soft matter science. In this symposium, 21 oral papers containing 16 invited papers and 14 poster papers from China, India, Korea, Taiwan, and Japan were presented during the three-day symposium. As a result of the review of poster and oral presentations of young scientists by symposium chairs, Dr Kummetha Raghunatha Reddy (Toyota Technological Institute) received the IUMRS-ICA 2008 Young Researcher Award. We are grateful to all invited speakers and many participants for valuable contributions and active discussions. Organizing committee of Symposium (IUMRS-ICA 2008) Professor Toshiji Kanaya (Kyoto University) Professor Kohji Tashiro (Toyota Technological Institute) Professor Kazuo Sakurai(Kitakyushu University) Professor Keiji Tanaka (Kyushu University) Dr Sono Sasaki (JASRI/Spring-8) Professor Naoya Torikai (KENS) Professor Moonhor Ree (POSTECH) Professor Kookheon Char (Seoul National University) Professor Charles C Han (CAS) Professor Atsushi Takahara(Kyushu University) Frontier of Polymeric Nano-Soft-Materials, Precision Polymer Synthesis, Self-assembling and Their Functionalization (Symposium Y of IUMRS-ICA2008) Seiichi Kawahara, Rong-Ming Ho, Hiroshi Jinnai, Masami Kamigaito, Takashi Miyata, Hiroshi Morita, Hideyuki Otsuka, Daewon Sohn, Keiji Tanaka It is our great pleasure and honor to publish peer-reviewed papers, presented in Symposium Y 'Frontier of Polymeric Nano-Soft-Materials Precision Polymer Synthesis, Self-assembling and Their Functionalization' at the International Union of Materials Research Societies International Conference in Asia 2008 (IUMRS-ICA2008), which was held on 9-13 December 2008, at Nagoya Congress Center, Nagoya, Japan. 'Polymeric nano-soft-materials' are novel outcomes based on a recent innovative evolution in polymer science, i.e. precision polymer synthesis, self-assembling and functionalization of multi-component systems. The materials are expected to exhibit specific functions and unique properties due to their hierarchic morphologies brought either by naturally-generated ordering or by artificial manipulation of the systems, e.g., crystallization and phase-separation. The emerging precision synthesis has brought out new types of polymers with well-controlled primary structures. Furthermore, the surface and interface of the material are recognized to play an important role in the outstanding mechanical, electrical and optical properties, which are required for medical and engineering applications. In order to understand structure-property relationships in the nano-soft-materials, it is indispensable to develop novel characterization techniques. Symposium Y aimed to provide recent advances in polymer synthesis, self-assembling processes and morpholog

Takahara, Atsushi; Kawahara, Seiichi

2009-09-01

229

Surface-grafted polymers from electrodeposited macroprecursors  

NASA Astrophysics Data System (ADS)

The use of electrochemically deposited macroprecursors for tethering polymers onto conducting surfaces is presented. Specifically, anodic electropolymerization was used as a tool to electrodeposit the precursors on electrodes that mediated the grafting of polymers onto surfaces. With this approach, patterning of surface-grafted polymers was also made possible through selective electrodeposition of the conjugated polymer network of the macroprecursors. This approach was used to fabricate protein and cell-resistant poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMEMA) brushes on Au surfaces. A chain transfer agent (CTA) was electrodeposited on the Au surface that served as the macroprecursor for the subsequent surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA). X-ray photoelectron spectroscopy (XPS) results showed the stability of the electrogenerated CTA under anodic conditions while successful brush growth was confirmed by surface techniques including XPS, ellipsometry, atomic force microscopy (AFM), and contact angle measurements. The PPEGMEMA-coated substrate exhibited protein and cell-repellant properties comparable to other reported PEG-functionalized surfaces. The proposed approach also yielded polymer-patterned surfaces as discussed in Chapters 3 and 4. An electroactive photocrosslinker was employed to facilitate the dual mode patterning of polystyrene (PS) on the surface by either electropatterning or photopatteming route. An electrodeposited CTA was also utilized to selectively grow surface-grafted PS on conducting regions of the substrate. Subsequent backfilling of nonconducting areas with a silane atom transfer radical polymerization (ATRP) initiator directed the growth of poly-N-isopropylacrylamide (PNIPAM) that produced a patterned binary polymer system. The patterns were successfully characterized by AFM and IR-imaging. Surface-grafted poly(N-vinyl carbazole) (PVK) film on indium tin oxide (ITO) was fabricated using this technique. This surface was used as a hole transporting layer (HTL) for a photovoltaic device as a possible replacement for existing poly(3,4-ethylene dioxythiophene) : poly(styrene sulfonate) (PEDOT:PSS). Device testing showed a comparable performance between the tethered PVK HTL and PEDOT:PSS as HTLs.

Rellamas Tria, Maria Celeste

230

Spinal bone graft - series (image)  

MedlinePLUS

... is made over the bone defect, and the bone graft is shaped around and inserted into the defect. The graft is held in place with pins, plates, or screws. The incisions are stitched (sutured) closed. A splint ...

231

Alveolar bone grafting.  

PubMed

In patients with cleft lip and palate, bone grafting in the mixed dentition in the residual alveolar cleft has become a well-established procedure. The main advantages can be summarised as follows: stabilisation of the maxillary arch; facilitation of eruption of the canine and sometimes facilitation of the lateral incisor eruption; providing bony support to the teeth adjacent to the cleft; raising the alar base of the nose; facilitation of closure of an oro-nasal fistula; making it possible to insert a titanium fixture in the grafted site and to obtain favourable periodontal conditions of the teeth within and adjacent to the cleft. The timing of the ABG surgery take into consideration not only eruption of the canine but also that of the lateral incisor, if present. The best time for bone grafting surgery is when a thin shell of bone still covers the soon erupting lateral incisor or canine tooth close to the cleft. PMID:19884665

Lilja, Jan

2009-10-01

232

Tailoring the properties of thermoplastic starch by blending with cinnamyl alcohol and radiation processing: An insight into the competitive grafting and scission reactions  

NASA Astrophysics Data System (ADS)

The present paper focuses on the effects of electron beam (EB) irradiation on thermoplastic materials based on destructurized starch including glycerol and water as plasticizers to assess the potentiality of cinnamyl alcohol as reactive additive capable of counterbalancing the degradation of the polysaccharide by inducing interchain covalent linkages. The tensile properties at break of test specimens of controlled composition submitted to EB irradiation at doses ranging from 50 to 200 kGy revealed the presence of competitive chain scission and bridging in samples containing cinnamyl alcohol at a relative concentration of 2.5% with regard to dry starch. The occurrence of crosslinking under particular conditions was evidenced by gel fraction measurements. The treatment under radiation was also applied to model blends including maltodextrin as a model for starch and the other ingredients to gain an insight into the radiation induced mechanisms at the molecular level. The presence of cinnamyl alcohol is found to limit degradation. Size exclusion chromatography and gel fraction allowed to monitor the effects and confirmed unambiguously the attachment of UV-absorbing chromophores onto the maltodextrin main chain. The combination of the obtained results demonstrates the possibility of altering in a favorable way the tensile properties of plasticized starch by applying high energy radiation to properly formulated blends including aromatic compounds like cinnamyl alcohol.

Khandal, Dhriti; Mikus, Pierre-Yves; Dole, Patrice; Bliard, Christophe; Soulestin, Jérémie; Lacrampe, Marie-France; Baumberger, Stéphanie; Coqueret, Xavier

2012-08-01

233

Grafting effects on vegetable quality  

Technology Transfer Automated Retrieval System (TEKTRAN)

In the United States, vegetable grafting is rare and few experiments have been done to determine optimal grafting procedures and production practices for different geographical and climatic regions in America. Grafting vegetables to control soilborne disease is a common practice in Asia, parts of E...

234

Bone Grafts in Craniofacial Surgery  

PubMed Central

Reconstruction of cranial and maxillofacial defects is a challenging task. The standard reconstruction method has been bone grafting. In this review, we shall describe the biological principles of bone graft healing, as pertinent to craniofacial reconstruction. Different types and sources of bone grafts will be discussed, as well as new methods of bone defect reconstruction. PMID:22110806

Elsalanty, Mohammed E.; Genecov, David G.

2009-01-01

235

Mixing in polymeric microfluidic devices.  

SciTech Connect

This SAND report describes progress made during a Sandia National Laboratories sponsored graduate fellowship. The fellowship was funded through an LDRD proposal. The goal of this project is development and characterization of mixing strategies for polymeric microfluidic devices. The mixing strategies under investigation include electroosmotic flow focusing, hydrodynamic focusing, physical constrictions and porous polymer monoliths. For electroosmotic flow focusing, simulations were performed to determine the effect of electroosmotic flow in a microchannel with heterogeneous surface potential. The heterogeneous surface potential caused recirculations to form within the microchannel. These recirculations could then be used to restrict two mixing streams and reduce the characteristic diffusion length. Maximum mixing occurred when the ratio of the mixing region surface potential to the average channel surface potential was made large in magnitude and negative in sign, and when the ratio of the characteristic convection time to the characteristic diffusion time was minimized. Based on these results, experiments were performed to evaluate the manipulation of surface potential using living-radical photopolymerization. The material chosen to manipulate typically exhibits a negative surface potential. Using living-radical surface grafting, a positive surface potential was produced using 2-(Dimethylamino)ethyl methacrylate and a neutral surface was produced using a poly(ethylene glycol) surface graft. Simulations investigating hydrodynamic focusing were also performed. For this technique, mixing is enhanced by using a tertiary fluid stream to constrict the two mixing streams and reduce the characteristic diffusion length. Maximum mixing occurred when the ratio of the tertiary flow stream flow-rate to the mixing streams flow-rate was maximized. Also, like the electroosmotic focusing mixer, mixing was also maximized when the ratio of the characteristic convection time to the characteristic diffusion time was minimized. Physical constrictions were investigated through simulations. The results show that the maximum mixing occurs when the height of the mixing region is minimized. Finally, experiments were performed to determine the effectiveness of using porous polymer monoliths to enhance mixing. The porous polymer monoliths were constructed using a monomer/salt paste. Two salt crystal size ranges were used; 75 to 106 microns and 53 to 180 microns. Mixing in the porous polymer monoliths fabricated with the 75 to 106 micron salt crystal size range was six times higher than a channel without a monolith. Mixing in the monolith fabricated with the 53 to 180 micron salt crystal size range was nine times higher.

Schunk, Peter Randall; Sun, Amy Cha-Tien; Davis, Robert H. (University of Colorado at Boulder, Boulder, CO); Brotherton, Christopher M. (University of Colorado at Boulder, Boulder, CO)

2006-04-01

236

Structure of poly(N-isopropylacrylamide) brushes and steric stability of their grafted cellulose nanocrystal dispersions.  

PubMed

Thermo-responsive poly(N-isopropylacrylamide) (poly(NIPAAm)) brushes were grafted from the surface of cellulose nanocrystals (CNC) via living radical polymerization (LRP) using different initiator and monomer concentrations. The dry film thickness of the poly(NIPAAm) layer around CNC was calculated based on Scanning Electron Microscopy (SEM) and dynamic light scattering (DLS) measurements. The wet film thicknesses of grafted poly(NIPAAm) brushes in water were calculated to be 15 and 9nm for NIPAAm-CNC-1 and NIPAAm-CNC-2, respectively. Grafted chain densities and wet film thicknesses at below and above the critical temperature (T=34°C) of polyNIPAAm were calculated by applying mean-field analytical theory. The non-ionic poly(NIPAAm) brushes screened the surface charges of CNC particles, leading to a significant decrease in the absolute zeta potential values for the poly(NIPAAm) grafted CNCs compared to the unmodified and initiator modified CNC samples. Nevertheless, the colloidal stability of poly(NIPAAm) grafted CNC particles were still maintained by steric stabilization below the critical temperature On the other side, hydrophobic attractions among poly(NIPAAm) grafted CNC rods above 34°C lead to coagulation and phase separation. While both poly(NIPAAm) grafted CNC samples showed thermo-responsive behavior, the reversibility of this temperature triggered property was dependent on grafting density. PMID:24998068

Hemraz, Usha D; Lu, Ang; Sunasee, Rajesh; Boluk, Yaman

2014-09-15

237

Rapid fabrication of polymeric micro lenses for optical fiber trapping and beam shaping  

NASA Astrophysics Data System (ADS)

This work reports a new type of optical fiber tweezers based on polymeric micro-lenses. The lenses are achieved by means of an economical and fast fabrication process, using an in-fiber photo-polymerization technique. The polymerization radiation is guided towards the fiber tip creating a polymeric waveguide. The method allows tailoring the geometry of the tip by adjusting the fabrication parameters. Furthermore, more complex shapes can be fabricated by exploring modal effects at the polymerization/trapping wavelengths, which can be used for different applications such as trapping, beam shaping and patterned illumination.

Rodrigues Ribeiro, R. S.; Queirós, R. B.; Ecoffet, C.; Soppera, O.; Oliva, A.; Guerreiro, A.; Jorge, P. A. S.

2014-09-01

238

Plasma polymerized high energy density dielectric films for capacitors  

NASA Technical Reports Server (NTRS)

High energy density polymeric dielectric films were prepared by plasma polymerization of a variety of gaseous monomers. This technique gives thin, reproducible, pinhole free, conformable, adherent, and insoluble coatings and overcomes the processing problems found in the preparation of thin films with bulk polymers. Thus, devices are prepared completely in a vacuum environment. The plasma polymerized films prepared all showed dielectric strengths of greater than 1000 kV/cm and in some cases values of greater than 4000 kV/cm were observed. The dielectric loss of all films was generally less than 1% at frequencies below 10 kHz, but this value increased at higher frequencies. All films were self healing. The dielectric strength was a function of the polymerization technique, whereas the dielectric constant varied with the structure of the starting material. Because of the thin films used (thickness in the submicron range) surface smoothness of the metal electrodes was found to be critical in obtaining high dielectric strengths. High dielectric strength graft copolymers were also prepared. Plasma polymerized ethane was found to be thermally stable up to 150 C in the presence of air and 250 C in the absence of air. No glass transitions were observed for this material.

Yamagishi, F. G.

1983-01-01

239

Controlling polymerization initiator concentration in mesoporous silica thin films.  

PubMed

We present a strategy toward controlled polymer density in mesopores by specifically adjusting the local amount of polymerization initiator at the pore wall. The polymerization initiator concentration as well as the polymer functionalization has a direct impact on mesoporous membrane properties such as ionic permselectivity. Mesoporous silica-based thin films were prepared with specifically adjusted amount of polymerization initiator (4-(3-triethoxysilyl)propoxybenzophenone (BPSilane)) or initiator binding functions ((3-aminopropyl)triethoxysilane (APTES)), directly and homogeneously incorporated into the silica wall pursuing a sol-gel-based co-condensation approach. The amount of polymerization initiator was adjusted by varying its concentration in the sol-gel precursor solution. The surface chemistry, porosity, pore accessibility, and reactivity of the surface functional groups were investigated by using infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray reflectometry, ellipsometry, atomic force microscopy, and transmission electron microscopy. We could gradually modify the amount of reactive polymerization initiators in these mesoporous membranes. Mesopores were maintained for APTES containing films for all tested ratios up to 25 mol % and for BPSilane containing films up to 15 mol %. These films showed accessible and charge-dependent ionic permselectivity and an increasing degree of functionalization with increasing precursor ratio. This approach can directly result in control of polymer grafting density in mesoporous films and thus has a direct impact on applications such as the control of ionic transport through mesoporous silica membranes. PMID:24364647

Krohm, Fabio; Didzoleit, Haiko; Schulze, Marcus; Dietz, Christian; Stark, Robert W; Hess, Christian; Stühn, Bernd; Brunsen, Annette

2014-01-14

240

Selective protection of polymeric materials from effects of chemical etching  

SciTech Connect

A photolithographic method for treating an article formed of polymeric material comprises subjecting portions of a surface of the polymeric article to ionizing radiation; and then subjecting the surface to chemical etching. The ionizing radiation treatment according to the present invention minimizes the effect of the subsequent chemical etching treatment. Thus, selective protection from the effects of chemical etching can be easily provided. The present invention has particular applicability to articles formed of fluorocarbons, such as PTFE. The ionizing radiation employed in the method may comprise Mg(k{alpha}) x-rays or low-energy electrons. 10 figs.

Martinez, R.J.; Rye, R.R.

1989-03-29

241

UV and electron beam-induced cationic polymerization  

NASA Astrophysics Data System (ADS)

This paper describes the basic photochemistry which has led to the development of rapid, efficient photoinitiators for UV-induced cationic polymerizations. These polymerizations are now widely employed in UV curing processes for such applications as coatings, adhesives and printing inks. The use of photosensitizers has enabled the extension of light-induced cationic polymerizations to the visible wavelength regions as well. Electron-beam irradiation is also capable of mediating the decomposition of cationic photoinitiators. The mechanism of this reaction involves reduction of the onium salt initiator by radicals generated by e-beam induced primary bond cleavage reactions. Rapid, efficient e-beam induced polymerizations at very low doses can be achieved through the use of specially designed monomers. The use of low energy electron beam radiation for thin film applications and high energy radiation to fabricate high performance carbon fiber reinforced epoxy resin matrix composites are described.

Crivello, James V.

1999-05-01

242

Injectable PolyHIPEs as High Porosity Bone Grafts  

PubMed Central

Polymerization of high internal phase emulsions (polyHIPEs) is a relatively new method for the production of high porosity scaffolds. The tunable architecture of these polyHIPE foams make them attractive candidates for tissue engineered bone grafts. Previously studied polyHIPE systems require either toxic diluents or high cure temperatures which prohibit their use as an injectable bone graft. In contrast, we have developed an injectable polyHIPE that cures at physiological temperatures to a rigid, high-porosity foam. First, a biodegradable macromer, propylene fumarate dimethacrylate (PFDMA), was synthesized that has appropriate viscosity and hydrophobicity for emulsification. The process of surfactant selection is detailed with particular focus on the key structural features of both polymer (log P values, hydrogen bond acceptor sites) and surfactant (HLB values, hydrogen bond donor sites) that enable stable HIPE formation. Incubation of HIPEs at 37°C was used to initiate radical crosslinking of the unsaturated double bond of the methacrylate groups to polymerize the continuous phase and lock in the emulsion geometry. The resulting polyHIPEs exhibited ~75% porosity, pore sizes ranging from 4 to 29 ?m, and an average compressive modulus and strength of 33 and 5 MPa, respectively. These findings highlight the great potential of these scaffolds as injectable, tissue engineered bone grafts. PMID:21861465

Moglia, Robert S.; Holm, Jennifer L.; Sears, Nicholas A.; Wilson, Caitlin J.; Harrison, Dawn M.; Cosgriff-Hernandez, Elizabeth

2011-01-01

243

Polymerization of vegetable oils  

SciTech Connect

The addition of antioxidants and dispersants is not sufficient to eliminate gum formation in vegetable oils. Even with relatively unsaturated oils like rapeseed the extent of unsaturation overwhelms these additives. Fuel deterioration during storage will be minimized in an anaerobic storage environment and, to a lesser extent, with a lower degree of oil unsaturation. Gum formation and carbon coking can also occur immediately preceding and during combustion. Thermal polymerization may be the dominant gum forming reaction under combustion conditions since thermal polymerization has a higher activation energy than oxidative polymerization and anaerobic conditions can occur within atomized fuel droplets. Carbon coking can be reduced with a lower degree of oil unsaturation and with better atomization of the fuel. 4 figures, 1 table.

Korus, R.A.; Mousetis, T.L.; Lloyd, L.

1982-01-01

244

Studies on graft copolymerization of gellan gum with N,N-dimethylacrylamide by the redox system.  

PubMed

The present paper reports the graft copolymerization of N,N-dimethylacrylamide onto gellan gumby free radical polymerization using potassium peroxymonosulphate/sarbose redox system in an inert atmosphere. The reaction conditions for maximum grafting have been optimized by varying the reaction variables, including the concentration of N,N-dimethylacrylamide(4.0×10(-2)-20×10(-2) mol dm(-3)), potassium peroxymonosulphate (0.6×10(-2)-1.4×10(-2)mol dm(-3)), sarbose (0.4×10(-3)-3.6×10(-3) mol dm(-3)), sulphuric acid (2.0×10(-3)-10×10(-3) mol dm(-3)), gellan gum (0.6-1.4 g dm(-3)) along with time duration (60-180 min) and temperature (25-45°C).Water-swelling capacity, metal ion sorption and flocculation studies of synthesized graft copolymer have been performed with respect to the parent polymer. The graft copolymer has been characterized by FTIR spectroscopy and thermogravimetric analysis. PMID:24984020

Pandey, Vijay Shankar; Verma, Shiv Kumar; Yadav, Mithilesh; Behari, Kunj

2014-09-01

245

A biocompatible calcium salt of hyaluronic acid grafted with polyacrylic acid.  

PubMed

We have synthesized hyaluronic acid (HA) grafted with polyacrylic acid (PAA) via controlled radical polymerization (CRP) in aqueous media. The grafted HA (HA-g-PAA) showed slow degradation by hyaluronidase compared with unmodified HA as a result of the steric hindrance produced by grafted PAA, and PAA was detached by hydrolysis and enzymatic degradation by lipase. It formed an insoluble salt immediately after mixing with Ca(2+) by the binding between grafted PAA and Ca(2+). Both HA-g-PAA and its salt showed good biocompatibility, especially to mesothelial cells in vitro. Finally, they were administered into mice subcutaneously and intraperitoneally. The residue of the material was observed 7 days after subcutaneous administration, while the material was almost cleared from the peritoneum 7 days after intraperitoneal administration with or without Ca(2+). HA-g-PAA is expected to be applicable to medical uses such as drug delivery in the peritoneum and for materials preventing peritoneal adhesion. PMID:25498607

Nakagawa, Yoshiyuki; Nakasako, Satoshi; Ohta, Seiichi; Ito, Taichi

2015-03-01

246

Temperature-induced chiral nematic phase changes of suspensions of poly( N , N -dimethylaminoethyl methacrylate)-grafted cellulose nanocrystals  

Microsoft Academic Search

Temperature-induced copolymers of poly(N,N-dimethylaminoethyl methacrylate)-grafted cellulose nanocrystals (PDMAEMA-grafted CNC) were synthesized by surface-initiated\\u000a atom transfer radical polymerization (ATRP). The graft copolymers were characterized by thermogravimetric analysis (TGA),\\u000a Fourier-transform infrared spectroscopy (FT-IR), and gel permeation chromatography (GPC). The size of the original CNC was\\u000a 10–40 nm in width and 100–400 nm in length, as characterized by atomic force microscopy (AFM). The liquid-crystalline properties

Jie Yi; Qunxing Xu; Xuefei Zhang; Hailiang Zhang

2009-01-01

247

Blood compatibility of AAc, HEMA, and PEGMA-grafted cellulose film  

NASA Astrophysics Data System (ADS)

To improve surface blood compatibility on cellulose film for hemodialysis, acrylic acid, 2-hydroxyethyl methacrylate and three kinds of polyethylene glycol methacrylates were grafted onto the cellulose film surface by radiation grafting technique. Heparin was introduced onto the grafted cellulose film surfaces. The grafting and heparinization were confirmed by Fourier transform infrared spectroscopy in the attenuated total reflectance mode and electron spectroscopy for chemical analysis. The blood compatibility of the modified cellulose film was examined by the determination of platelet adhesion and thrombus formation.

Nho, Young Chang; Kwon, Oh Hyun

2003-03-01

248

Current status of arterial grafts for coronary artery bypass grafting  

PubMed Central

For over a decade there has been accumulating evidence that the use of more than a single arterial graft during coronary artery bypass grafting can improve clinical outcomes. However the vast majority of patients in most developed countries still only receive a single arterial conduit even in the presence of multivessel coronary artery disease. This review summarizes the current evidence for the use of a second internal mammary artery and/or radial artery graft. While in comparison to vein grafts the superior patency of internal mammary artery grafts is well established, there now exists strong and consistent evidence of the superior patency of radial arteries over the longer term. Likewise, there is a rapidly growing body of evidence that the superior patency of both these arteries in comparison to vein grafts translates into improved clinical outcomes. PMID:23977618

2013-01-01

249

Kinetics of Emulsion Polymerization  

Microsoft Academic Search

As a basis for understanding emulsion polymerization, the kinetics of free radical reactions in isolated loci is discussed subject to the condition that the free radicals are supplied to the loci from an external source. Three cases of interest are considered: that in which the average number of free radicals per locus is small compared with unity, that in which

Wendell V. Smith; Roswell H. Ewart

1948-01-01

250

Responsive polymeric delivery systems  

Microsoft Academic Search

This paper discusses the state of the art in a relatively new approach in the field of controlled drug delivery–responsive polymeric drug delivery systems. Such systems are capable of adjusting drug release rates in response to a physiological need. The fundamental principles of externally and self-regulated delivery systems are examined. Special attention is paid to specific clinical settings such as

Joseph Kost; Robert Langer

2001-01-01

251

Encapsulated cell grafts to treat cellular deficiencies and dysfunction.  

PubMed

Cell transplantation provides a therapeutic alternative to whole organ transplantation in the management of diseases arising from the absence or failure of specialized cells. Though allogenic transplantation is favorable in terms of graft acceptance, xenotransplantation can provide a potentially unlimited source of cells and can overcome shortage of human donors. Effective immunoisolation of the xenografts is critical for their long term survival and function. Encapsulation of cells in polymeric matrices, organic or inorganic, provides a physical selectively permeable barrier between the host and the graft, thereby immunoisolating the graft. Microencapsulation of cells in alginate hydrogels has been pervasive, but this approach does not provide precise control over porosity, whereas micro- and nano-fabrication technologies can provide precise and reproducible control over porosity. We highlight both encapsulation approaches in this review, with their relative advantages and challenges. We also highlight the therapeutic potential of encapsulated cells for treating a variety of diseases, detailing the xenotransplantation of pancreatic islets in diabetes therapy as well as the grafting of engineered cells that facilitate localized enzyme-prodrug therapy of pancreatic cancer. PMID:22196222

Krishnamurthy, N V; Gimi, Barjor

2011-01-01

252

Siloxane-grafted membranes  

DOEpatents

Composite cellulosic semipermeable membranes are disclosed which are the covalently bonded reaction product of an asymmetric cellulosic semipermeable membrane and a polysiloxane containing reactive functional groups. The two reactants chemically bond by ether, ester, amide or acrylate linkages to form a siloxane-grafted cellulosic membrane having superior selectivity and flux stability. Selectivity may be enhanced by wetting the surface with a swelling agent such as water.

Friesen, Dwayne T. (Bend, OR); Obligin, Alan S. (Catonville, MD)

1989-01-01

253

Siloxane-grafted membranes  

DOEpatents

Composite cellulosic semipermeable membranes are disclosed which are the covalently bonded reaction product of an asymmetric cellulosic semipermeable membrane and a polysiloxane containing reactive functional group. The two reactants chemically bond by ether, ester, amide or acrylate linkages to form a siloxane-grafted cellulosic membrane having superior selectivity and flux stability. Selectivity may be enhanced by wetting the surface with a swelling agent such as water.

Friesen, D.T.; Obligin, A.S.

1989-10-31

254

Grafting of GMA and some comonomers onto chitosan for controlled release of diclofenac sodium.  

PubMed

In order to develop pH sensitive hydrogels for controlled drug release we have graft copolymerized glycidyl methacrylate (GMA) with comonomers acrylic acid, acrylamide and acrylonitrile, onto chitosan (Ch) by using potassium persulphate (KPS) as free radical initiator in aqueous solution. The optimum percent grafting for GMA was recorded for 1g chitosan at [KPS]=25.00 × 10(-3)mol/L, [GMA]=0.756 × 10(-3)mol/L, reaction temperature=60 °C and reaction time=1h in 20 mL H2O. Binary monomers were grafted for five different concentrations at optimum grafting conditions evaluated for GMA alone onto chitosan. The graft copolymers were characterized by FTIR, XRD, TGA and SEM. The swelling properties of chitosan and graft copolymers were investigated at different pH to define their end uses in sustained release of an anti-inflammatory drug, diclofenac sodium. Percent drug release w.r.t. drug loaded in polymeric sample was studied as function of time in buffer solutions of pH 2.0 and 7.4. In vitro release data was analyzed using Fick's Law. Chitosan grafted with binary monomers, GMA-co-AAm and GMA-co-AN showed very good results for sustained release of drug at 7.4 pH. PMID:24374084

Sharma, Rajeev Kr; Lalita; Singh, Anirudh P; Chauhan, Ghanshyam S

2014-03-01

255

Ion-exchanger synthesis using reversible addition-fragmentation chain transfer polymerization.  

PubMed

An ion-exchanger with polyanionic molecular brushes was synthesized by a "grafting from" route based on "surface-controlled reversible addition-fragmentation chain transfer polymerization" (RAFT). The RAFT agent, PhC(S)SMgBr was covalently attached to monodisperse-porous poly(dihydroxypropyl methacrylate-co-ethylene dimethacrylate), poly(DHPM-co-EDM) particles 5.8 microm in size. The monomer, 3-sulfopropyl methacrylate (SPM), was grafted from the surface of poly(DHPM-co-EDM) particles with an immobilized chain transfer agent by the proposed RAFT protocol. The degree of polymerization of SPM (i. e. the molecular length of the polyanionic ligand) on the particles was controlled by varying the molar ratio of monomer/RAFT agent. The particles carrying polyanionic molecular brushes with different lengths were tested as packing material in the separation of proteins by ion exchange chromatography. The columns packed with the particles carrying relatively longer polyanionic ligands exhibited higher separation efficiency in the separation of four proteins. Plate heights between 130-200 microm were obtained. The ion-exchanger having poly-(SPM) ligand with lower degree of polymerization provided better peak-resolutions on applying a salt gradient with higher slope. The molecular length and the ion-exchanger group content of polyionic ligand were adjusted by controlling the degree of polymerization and the grafting density, respectively. This property allowed control of the separation performance of the ion-exchanger packing. PMID:19479766

Unsal, Ender; Uguzdogan, Erdal; Patir, Süleyman; Tuncel, Ali

2009-06-01

256

Influence of the polymeric interphase design on the interfacial properties of (fiber-reinforced) composites.  

PubMed

In fiber-reinforced composites, the interphase nanostructure (i.e., the extended region between two phases in contact) has a pronounced influence on their interfacial adhesion. This work aims at establishing a link between the interphase design of PS-based polymeric fiber coatings and their influence on the micromechanical performance of epoxy-based composite materials. Thiol-ene photochemistry was utilized to introduce a polymeric gradient on silica-like surfaces following a two-step approach without additional photoinitiator. Two complementary grafting-techniques were adapted to modify glass fibers: "Grafting-onto" deposition of PB-b-PS diblock copolymers for thin-film coatings (thickness<20 nm) at low grafting density (<0.1 chains/nm2)--and "grafting-from" polymerization for brush-like PS homopolymer coatings of higher thickness (up to 225 nm) and higher density. Polymer-coated glass fibers were characterized for polymer content using thermogravimetric analysis (TGA) and their nanostructural morphologies by scanning electron microscopy (SEM). Model substrates of flat glass and silicon were studied by atomic force microscopy (AFM) and spectroscopic ellipsometry (SE). The change in interfacial shear strength (IFSS) due to fiber modification was determined by a single fiber pull-out experiment. Thick coatings (>40 nm) resulted in a 50% decrease in IFSS. Higher shear strength occurred for thinner coatings of homopolymer and for lower grafting densities of copolymer. Increased IFSS (10%) was found upon dilution of the surface chain density by mixing copolymers. We show that the interfacial shear strength can be increased by tailoring of the interphase design, even for systems with inherently poor adhesion. Perspectives of polymeric fiber coatings for tailored matrix-fiber compatibility and interfacial adhesion are discussed. PMID:23446425

Kuttner, Christian; Hanisch, Andreas; Schmalz, Holger; Eder, Michaela; Schlaad, Helmut; Burgert, Ingo; Fery, Andreas

2013-04-10

257

Complex cervical spine neoplastic disease: reconstruction after surgery by using a vascularized fibular strut graft. Case report.  

PubMed

The authors report a case of an aggressive chordoma in the cervical spine of a 15-year-old girl who underwent radical resection followed by reconstruction using an anterior vascularized fibular strut graft and posterior arthrodesis prior to receiving immediate postoperative radiation therapy. The patient had successful graft incorporation 4 months postoperatively. The authors review the advantages of using vascularized fibular strut grafts for the treatment of multilevel cervical spine neoplastic disease and discuss the theoretical advantages of using vascularized grafts that tolerate therapeutic levels of radiation. PMID:10413139

Wright, N M; Kaufman, B A; Haughey, B H; Lauryssen, C

1999-01-01

258

Radiation effect on poly ( p-sodium styrene sulphonate) of different degrees of polymerization in aqueous solution: pulse radiolysis and steady state study  

NASA Astrophysics Data System (ADS)

Radiation induced effects on poly ( p-sodium styrene sulphonate) (PSSS) of two molecular weights, namely 10 6 and 70,000 in aqueous solution have been investigated by steady state and pulse radiolysis (PR) techniques. The reactions of primary radicals of water radiolysis such as OH radical, e aq-, H atom, some oxidizing radicals like N 3rad , Cl 2rad - and SO 4rad - and reducing species like CO 2rad - with PSSS have been investigated. The results indicate that the reactivity of these species towards PSSS is a function of molecular weight of PSSS. The absorption spectra of transient species produced when dilute aqueous solutions of PSSS of different molecular weights are subjected to pulse radiolysis have been compared. Rate constants for the reaction of OH radical and H atom with PSSS have been evaluated both by competition kinetics method and by direct observation of build up of transient species. The results indicate that OH radical and H atom react with PSSS in different ways. Near neutral pH, the OH radical reacts with substituted pendant aromatic ring of the PSSS to form an adduct, with a rate constant of 5.5×10 8 and 1.1×10 9 dm 3 mol -1 s -1 for PSSS of molecular weights 10 6 and 70,000, respectively. H atom on the other hand abstracts H atom from the PSSS backbone as well as forms an adduct by reacting with aromatic ring. The rate constant values for reaction of aqueous electron with PSSS were found to be 5×10 7 dm 3 mol -1 s -1 ( Mw=10 6) and 2.2×10 8 dm 3 mol -1 s -1 ( Mw=70,000). The anion formed did not transfer electron to methyl viologen in the pH range of 6-10.5. The viscosity of the aqueous PSSS solution decreases with irradiation, up to doses of 1000 kGy indicating degradation of PSSS in this dose range. The PSSS of higher molecular weight is more prone to degradation. The chain scission is a function of dose rate, concentration of polymer and ambient of irradiation. At doses beyond ˜2500 kGy there is a sharp increase in viscosity of the PSSS solutions till the solutions set to a soft, sticky gel mass. The gelation dose ( Dgel) is a function of molecular weight of the polymer and initial polymer concentration. In the presence of crosslinking agent like N, N-methylene bis acrylamide, the gelation was faster for PSSS of higher molecular weight. Gelation was most efficient for 20% (w/w) polymer concentration.

Bhardwaj, Y. K.; Mohan, H.; Sabharwal, S.; Mukherjee, T.

2001-09-01

259

Radiation  

Cancer.gov

DCEG researchers carry out a broad-based research program designed to identify, understand, and quantify the risk of cancer in populations exposed to medical, occupational, or environmental radiation. They study ionizing radiation exposures (e.g., x-rays,

260

Synthesis of poly(acrylamide)-starch and hydrolyzed starch graft copolymers as a size base material for cotton textiles  

Microsoft Academic Search

Rice starch was hydrolyzed with HCl to obtain starch with different molecular sizes. The original starch and hydrolyzed starches derived from it were independently graft copolymerized with acrylamide (Aam) using potassium permanganate\\/citric acid as initiator under different conditions of initiator and monomer concentration, polymerization time and temperature. The newly synthesized products were applied to sizing of cotton textiles to see

Kh. M. Mostafa

1997-01-01

261

What Is Coronary Artery Bypass Grafting (CABG)?  

MedlinePLUS

... Medical Illustrations: Jill Rhead, MA What is Coronary Artery Bypass Grafting (CABG)? What Can Happen When Blockages ... Condition be Like After CABG? WHAT IS CORONARY ARTERY BYPASS GRAFTING (CABG)? Coronary artery bypass grafting or " ...

262

SURFACE-INITIATED ATOM TRANSFER RADICAL POLYMERIZATION AS A TOOL FOR COATING OF VARIOUS SURFACES WITH FLUOROPOLYMERS  

E-print Network

SURFACE-INITIATED ATOM TRANSFER RADICAL POLYMERIZATION AS A TOOL FOR COATING OF VARIOUS SURFACES the covalent grafting, and thus the coating of the fibers with PFS. Depending on the surface area of the used monomers to cellulose,3 were now successfully followed by surface-initiated ATRP of pentafluorostyrene (FS

263

Frontal Polymerization in Microgravity  

NASA Technical Reports Server (NTRS)

Frontal polymerization systems, with their inherent large thermal and compositional gradients, are greatly affected by buoyancy-driven convection. Sounding rocket experiments allowed the preparation of benchmark materials and demonstrated that methods to suppress the Rayleigh-Taylor instability in ground-based research did not significantly affect the molecular weight of the polymer. Experiments under weightlessness show clearly that bubbles produced during the reaction interact very differently than under 1 g.

Pojman, John A.

1999-01-01

264

Self-assembly of well-defined polyacrylamide-polystyrene copolymer on fibrillar clays via ultrasonic-assisted surface-initiated atom transfer radical polymerization.  

PubMed

Well-defined polyacrylamide-polystyrene copolymers were grafted from the fibrillar clay, attapulgite, by a four-step self-assembly process: (i) the gamma-aminopropyltriethoxyl silane was self-assembled onto the surfaces of the attapulgite; (ii) the surface amino groups were amidated with bromoacetylbromide; (iii) the bromo-acetamide modified attapulgite was used as macro-initiator for the surface-initiated atom transfer radical polymerization of styrene with the catalyst of the complex of 1,10-phenanthroline and Cu(I)Br; (iv) the polystyrene grafted attapulgite was then used as macroinitiator for the polymerization of acrylamide. The two steps of the surface-initiated atom transfer radical polymerizations were all conducted under ultrasonic irradiation at room temperature. The product, polyacrylamide-polystyrene copolymers grafted attapulgite, had been characterized with elemental analysis, Fourier transform infrared spectroscopy, Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy, X-ray diffractometry, and transmission electron microscopy. PMID:17025071

Liu, Peng; Wang, Tingmei; Su, Zhixing

2006-06-01

265

Alar cartilage grafts.  

PubMed

The alar cartilages provide the contour and structural support of the nasal tip. Current rhinoplasty concepts support preservation of alar structure with suture techniques or judicious cephalic trim indicated for tip deformities. In many primary cases and some revisions, adequate alar structure exists to achieve the desired aesthetic and functional results with conservative surgical methods. In some primary and most revision cases, however, the existing tip structure is inadequate to create a structurally sound and aesthetically pleasing nasal tip without adding structure. In these cases, alar cartilage grafting techniques are indicated to recapitulate nasal tip contour and structure. PMID:20206743

Weber, Stephen M; Baker, Shan R

2010-04-01

266

ACL Reconstruction: Choosing the Graft  

PubMed Central

Summary Rupture of the anterior cruciate ligament is one of the most common ligament injuries in sports traumatology. The need for surgical anterior cruciate ligament reconstruction is justified by its anatomical characteristics. Key considerations when choosing a graft include the potential for bone integration and the risk of failure. Bone sclerosis around the tunnel affects the integration of the graft. For this reason, one aspect upon which orthopedic surgeons should focus is the biology of the bone-graft interface. Although the BPTB graft is still used, hamstrings and synthetic grafts have become increasingly widespread and popular over the years. An allograft certainly requires more long-term follow-up to validate its use in response to functional, clinical and biological requirements.

Cerulli, Giuliano; Placella, Giacomo; Sebastiani, Enrico; Tei, Matteo Maria; Speziali, Andrea; Manfreda, Francesco

2013-01-01

267

Polymeric salt bridges for conducting electric current in microfluidic devices  

DOEpatents

A "cast-in-place" monolithic microporous polymer salt bridge for conducting electrical current in microfluidic devices, and methods for manufacture thereof is disclosed. Polymeric salt bridges are formed in place in capillaries or microchannels. Formulations are prepared with monomer, suitable cross-linkers, solvent, and a thermal or radiation responsive initiator. The formulation is placed in a desired location and then suitable radiation such as UV light is used to polymerize the salt bridge within a desired structural location. Embodiments are provided wherein the polymeric salt bridges have sufficient porosity to allow ionic migration without bulk flow of solvents therethrough. The salt bridges form barriers that seal against fluid pressures in excess of 5000 pounds per square inch. The salt bridges can be formulated for carriage of suitable amperage at a desired voltage, and thus microfluidic devices using such salt bridges can be specifically constructed to meet selected analytical requirements.

Shepodd, Timothy J. (Livermore, CA); Tichenor, Mark S. (San Diego, CA); Artau, Alexander (Humacao, PR)

2009-11-17

268

Viability of cartilage grafts in various forms.  

PubMed

The viability of cartilage grafts, in many forms, has been researched since the using of cartilage grafts in surgical procedures. Cryopreservation period and viability of cartilage grafts have remained unclear. This study was performed to investigate the durability, viability, and behavior of fresh or cryopreserved cartilage grafts when used as autografts or allografts in various forms.Six cartilage grafts (1 of each preparation type; 3 blocks and 3 diced) were prepared by wrapping with Surgicel or autogenous fascia, or they were left bare. After the graft preparation stage, the cartilage grafts were inserted into pockets prepared on the dorsum of each rabbit. Groups 1, 2, 3, and 4 (6 rabbits in each group) received autogenous fresh grafts, allogenous fresh grafts, autogenous cryopreserved grafts, and allogenous cryopreserved grafts, respectively. All cartilage grafts were implanted for 2 months.At the end of the second month, specimens were harvested and analyzed. The bare grafts provided the most viable specimens. There was no significant difference between the frozen or fresh and allograft or autograft groups with respect to viability and resorption ratios. The bare block graft, in all groups, survived significantly more than the other graft types.Allografts (homografts), similar autografts, did not create major problems, and they had excellent host tolerance and low antigenicity, especially when the perichondrium was removed. Viability and durability of the bare grafts (diced and block) were better than fascia or Surgicel-wrapped cartilage graft forms. PMID:21959409

Firat, Cemal; Gurlek, Ali; Aydin, Nasuhi Engin; Aydn, Nasuhi Engin

2011-09-01

269

Novel Synthesis of Surface-Grafted Radical Initiator With Improved Stability and Yield  

NASA Astrophysics Data System (ADS)

Polymers grafted at interfaces are attractive for applications including antifouling coatings, biologically functionalized materials, and responsive surfaces. The ``grafting from'' approach to form densely packed brushes involves functionalizing a substrate with initiating moieties, and carrying out polymerization, e.g., surface-inititated free-radical polymerization (SI-FRP). Azo initiators for SI-FRP are commonly synthesized by a low-yielding route requiring large amounts of potassium cyanide. Those initiators are linked to a substrate by means of an ester group, rendering tethered polymers susceptible to degrafting by hydrolysis. We present a novel synthetic route to an asymmetric azo initiator, whose yield is nearly double that of previous syntheses. Cyanide usage in the new method is reduced by 72 percent. The spacer linking the initiator to a substrate contains only carbon-carbon bonds, resulting in stable brushes. Results are demonstrated for SI-FRP as well as reverse ATRP and RAFT.

Bain, Erich; Dawes, Keith; Hu, Xinfang; Gorman, Christopher; Srogl, Jiri; Genzer, Jan

2012-02-01

270

Modular Modification of Polymeric Microspheres.  

E-print Network

??Die vorliegende Arbeit beschreibt die vielseitige Modifikation von polymeren Mikrokugeln mit Polymeren. Die Polymere, darunter auch Glucopolymere, wurden durch die kontrollierte RAFT-Polymerisation erhalten. Die Funktionalisierung… (more)

Kaupp, Michael

2014-01-01

271

Chitosan-graft-spermine as a gene carrier in vitro and in vivo  

Microsoft Academic Search

Chitosan has been proposed as a non-viral gene carrier because of its biodegradable and biocompatible cationic polymeric properties. However, the transfection efficiency of chitosan-DNA complexes is still too low for clinical trials. To improve transfection efficiency, we prepared a chitosan-graft-spermine (CHI-g-SPE) copolymer by an imine reaction between periodate-oxidized chitosan and spermine. The CHI-g-SPE copolymer was complexed with plasmid DNA in

Hu-Lin Jiang; Hwang-Tae Lim; You-Kyoung Kim; Rohidas Arote; Ji-Young Shin; Jung-Taek Kwon; Ji-Eun Kim; Ji-Hye Kim; Duyeol Kim; Chanhee Chae; Jae-Woon Nah; Yun-Jaie Choi; Chong-Su Cho; Myung-Haing Cho

2011-01-01

272

Synthesis and characterization of polycationic chitosan- graft-poly (l-lysine)  

Microsoft Academic Search

A type of polysaccharide\\/polypeptide hydride material, chitosan derivatives with polypeptide side chains, was prepared via ring-opening polymerization of N?-carbobenzyloxy-l-lysine NCA initiated by water-soluble chitosan and followed by removing the side-chain protective groups. The graft polymer was investigated through FTIR spectroscopy, proton nuclear magnetic resonance spectroscopy and X-ray diffraction to confirm the structure. Furthermore, the results of the atomic force microscopy

Ping Chi; Jing Wang; Changsheng Liu

2008-01-01

273

Surface grafting of microfibrillated cellulose with poly( ?-caprolactone) – Synthesis and characterization  

Microsoft Academic Search

In cellulose nanocomposites, the surface of the nanocellulosic phase is critical with respect to nanocellulose dispersion, network formation and nanocomposite properties. Microfibrillated cellulose (MFC) has been grafted with poly(?-caprolactone) (PCL), via ring-opening polymerization (ROP). This changes the surface characteristics of MFC and makes it possible to obtain a stable dispersion of MFC in a nonpolar solvent; it also improves MFC’s

Hanna Lönnberg; Linda Fogelström; Lars Berglund; Eva Malmström; Anders Hult

2008-01-01

274

Surface grafting of microfibrillated cellulose with poly(e-caprolactone) - Synthesis and characterization  

Microsoft Academic Search

a b s t r a c t In cellulose nanocomposites, the surface of the nanocellulosic phase is critical with respect to nanocellulose dispersion, network formation and nanocomposite properties. Microfibr- illated cellulose (MFC) has been grafted with poly(e-caprolactone) (PCL), via ring-opening polymerization (ROP). This changes the surface characteristics of MFC and makes it possi- ble to obtain a stable dispersion

Hanna Lönnberg; Azizi Samir; Lars Berglund; Eva Malmström; Anders Hult

2008-01-01

275

Interpolymer reaction between antimicrobial polycation and polyanions grafted to cellulose fibre  

Microsoft Academic Search

The characteristics and features of the interpolymer reaction (IPR) between a polymeric antimicrobial substance (AS) containing basic groups — poly-1,2-dimethyl-5-vinylpyridinium methylsulfate (PDMVPMS), and graft copolymers of cellulose of varying structure containing acid groups (C-gr-PAA-Na, C-gr-PMAA-Na, C-gr-PSSA-Na) were established. It was found that with a high bath modulus, IPR takes place for a long time; the structure of the polyanion chain

M. A. Penenzhik; I. S. Ryshkina; A. D. Virnik

1996-01-01

276

Biotribological properties of UHMWPE grafted with AA under lubrication as artificial joint.  

PubMed

Osteolysis caused by wear particles from polyethylene in the artificial hip joints is a serious issue. In order to endow the low friction and wear of the bearing surface of ultra-high molecular weight polyethylene (UHMWPE) artificial joint for a longer term, hydrophilic acrylic acid (AA) was grafted on UHMWPE powders with the method of ultraviolet irradiation and then the modified powders were hot pressed. The tribological properties of modified UHMWPE sliding against CoCrMo metallic plate on reciprocating tribometer under calf serum, saline and distilled water lubrication during a long-term friction were investigated. The measurement of Fourier-transform infrared spectroscopy indicates that AA is successfully grafted on the surface of UHMWPE powders by photo-induced graft polymerization. Contact angles of UHMWPE are decreased from 83° to 35° by grafting and the surface wettability is effectively improved. The tensile strength of modified sample decreases. The friction coefficient and wear rate of UHMWPE-g-PAA under calf serum, saline and distilled water lubrication are lower than that of untreated UHMWPE. With the increase of grafting ratio, the wear rate of UHMWPE-g-PAA decreases firstly and then increases. The modified UHMWPE with grafting ratio of 3.5 % has the lowest wear rate, which is just quarter of the untreated UHMWPE. The hydrated PAA polymer brushes enclosed in the UHMWPE bulk material provide continuous lubrication during long term sliding. PMID:23793532

Deng, Yaling; Xiong, Dangsheng; Wang, Kun

2013-09-01

277

Hydrolyzed polyacrylamide grafted maize starch based microbeads: application in pH responsive drug delivery.  

PubMed

The present study details the synthesis, characterization and pharmaceutical application of hydrolysed polyacrylamide grafted maize starch (HPam-g-MS) as promising polymeric material for the development of pH responsive microbeads. Different grades of graft copolymer were synthesized by changing the net microwave irradiation time, while keeping all other factors constant. Acute oral toxicity study performed in rodents ensured the bio-safety of graft copolymer for clinical application. Various batches of aceclofenac loaded microbeads were prepared by ionic gelation method using synthesized graft copolymers and evaluated for formulation parameters. FTIR spectroscopy confirmed the chemical compatibility between drug and graft copolymer. Results of in vitro release study (USP type-II) carried out in two different pH media (pH 1.2 acid buffer and pH 7.4 phosphate buffer) showed that release rate of drug from developed microbeads was a function of both: (a) surrounding pH and (b) the matrix composition. The drug release was relatively higher at alkaline pH as compared to acidic pH and this feature is desirable from viewpoint of site specific drug delivery. A direct correlation was observed between percentage grafting and microbeads performance and it presents a scope for further research on application and optimization of HPam-g-MS based microbeads as drug delivery carriers. PMID:24971555

Setty, C Mallikarjuna; Deshmukh, Anand S; Badiger, Aravind M

2014-09-01

278

Living olefin polymerization processes  

DOEpatents

Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

Schrock, Richard R. (Winchester, MA); Baumann, Robert (Cambridge, MA)

1999-01-01

279

Living olefin polymerization processes  

DOEpatents

Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

Schrock, R.R.; Baumann, R.

1999-03-30

280

Bimorphic polymeric photomechanical actuator  

NASA Technical Reports Server (NTRS)

A bimorphic polymeric photomechanical actuator, in one embodiment using polyvinylidene fluoride (PVDF) as a photosensitive body, transmitting light over fiber optic cables, and controlling the shape and pulse duration of the light pulse to control movement of the actuator. Multiple light beams are utilized to generate different ranges of motion for the actuator from a single photomechanical body and alternative designs use multiple light beams and multiple photomechanical bodies to provide controlled movement. Actuator movement using one or more ranges of motion is utilized to control motion to position an actuating element in three dimensional space.

Sarkisov, Sergey S. (Inventor); Curley, Michael J. (Inventor); Adamovsky, Grigory (Inventor); Sarkisov, Jr., Sergey S. (Inventor); Fields, Aisha B. (Inventor)

2006-01-01

281

Robot-Assisted Antegrade In-Situ Fenestrated Stent Grafting  

SciTech Connect

To determine the technical feasibility of a novel approach of in-situ fenestration of aortic stent grafts by using a remotely controlled robotic steerable catheter system in the porcine model. A 65-kg pig underwent robot-assisted bilateral antegrade in-situ renal fenestration of an abdominal aortic stent graft with subsequent successful deployment of a bare metal stent into the right renal artery. A 16-mm iliac extension covered stent served as the porcine aortic endograft. Under fluoroscopic guidance, the graft was punctured with a 20-G customized diathermy needle that was introduced and kept in place by the robotic arm. The needle was exchanged for a 4 x 20 mm cutting balloon before successful deployment of the renal stent. Robot-assisted antegrade in-situ fenestration is technically feasible in a large mammalian model. The robotic system enables precise manipulation, stable positioning, and minimum instrumentation of the aorta and its branches while minimizing radiation exposure.

Riga, Celia V., E-mail: c.riga@imperial.ac.uk; Bicknell, Colin D. [Imperial College Healthcare, St Mary's Hospital, Regional Vascular Unit (United Kingdom); Wallace, Daniel [Hansen Medical (United States); Hamady, Mohamad; Cheshire, Nicholas [Imperial College Healthcare, St Mary's Hospital, Regional Vascular Unit (United Kingdom)

2009-05-15

282

Space environmental effects on polymeric materials  

NASA Technical Reports Server (NTRS)

Polymer-matrix composites have considerable potential for use in the construction of orbiting structures such as the space station and space antennas because of their light weight, high strength, and low thermal expansion. However, they can suffer surface erosion by interaction with atomic oxygen in low-Earth orbit and degradation and/or embrittlement by electrons and ultraviolet radiation especially in geosynchronous orbit. Thus, a study of the effect of these environmental hazards on polymeric materials is an important step in the assessment of such materials for future use in space.

Kiefer, Richard L.; Orwoll, Robert A.

1988-01-01

283

On the mechanisms of radiation-induced curing of epoxy-fiber composites  

NASA Astrophysics Data System (ADS)

Depending on the monomer molecular structure, the mechanisms of radiation-induced polymerization proceed via either C-centered radical mechanisms or cationic polymerization. While polymerization via C-centered radicals can be impeded by the presence of oxygen and high dose-rate, polymerization through cationic polymerization is inhibited even by the presence of trace amounts of water. Synergy by the combination of radiation and thermal curing can help to achieve various desired properties of polymer-fiber composite materials.

Al-Sheikhly, Mohamad; McLaughlin, William L.

1996-08-01

284

Organometallic Polymeric Conductors  

NASA Technical Reports Server (NTRS)

For aerospace applications, the use of polymers can result in tremendous weight savings over metals. Suitable polymeric materials for some applications like EMI shielding, spacecraft grounding, and charge dissipation must combine high electrical conductivity with long-term environmental stability, good processability, and good mechanical properties. Recently, other investigators have reported hybrid films made from an electrically conductive polymer combined with insulating polymers. In all of these instances, the films were prepared by infiltrating an insulating polymer with a precursor for a conductive polymer (either polypyrrole or polythiophene), and oxidatively polymerizing the precursor in situ. The resulting composite films have good electrical conductivity, while overcoming the brittleness inherent in most conductive polymers. The highest conductivities reported (approximately 4/Scm) were achieved with polythiophene in a polystyrene host polymer. The best films using a polyamide as base polymer were four orders of magnitude less conductive than the polystyrene films. The authors suggested that this was because polyimides were unable to swell sufficiently for infiltration of monomer as in the polystyrene. It was not clear, however, if the different conductivities obtained were merely the result of differing oxidation conditions. Oxidation time, temperature and oxidant concentration varied widely among the studies.

1997-01-01

285

Unusual costochondral bone graft complication.  

PubMed

In hemifacial microsomia, patients with severely hypoplastic mandibles (Pruzansky type III) require replacement of the ramus and condyle unit. Common complications of this procedure include graft fracture and overgrowth of the graft. An uncommon case of osteolysis of the costochondral graft with osteitis of the middle cranial fossa is reported herein. To our knowledge, no such case has been reported in the literature previously. The aim of this report is to present the only known case and to discuss the contributing factors. PMID:23972557

Tabchouri, Nathalie; Kadlub, Natacha; Diner, Patrick A; Picard, Arnaud

2013-11-01

286

Polysulfone functionalized with phosphonated poly(pentafluorostyrene) grafts for potential fuel cell applications.  

PubMed

A multi-step synthetic strategy to polysulfone (PSU) grafted with phosphonated poly(pentafluorostyrene) (PFS) is developed. It involves controlled radical polymerization resulting in alkyne-end functional PFS. The next step is the modification of PSU with a number of azide side groups. The grafting of PFS onto PSU backbone is performed via the "click"-chemistry approach. In a final step, the PFS-grafts are subjected to the post phosphonation. The copolymers are evaluated as membranes for potential fuel cell applications through thermal analyses, water uptake, and conductivity measurements. The proposed synthetic route opens the possibility to tune copolymers' hydrophilic-hydrophobic balance to obtain membranes with an optimal balance between proton conductivity and mechanical properties. PMID:22623205

Dimitrov, Ivaylo; Takamuku, Shogo; Jankova, Katja; Jannasch, Patric; Hvilsted, Søren

2012-08-28

287

Binary mixed homopolymer brushes grafted on nanorod particles: A self-consistent field theory study  

SciTech Connect

We employ the self-consistent field theory to study phase structures of brush-rod systems composed of two chemically distinct linear homopolymers. The polymer chains are uniformly grafted on the surface of a nanorod particle of finite length and comparable radius to the polymer radius of gyration. A “masking” technique treating the cylindrical boundary is introduced to solve the modified diffusion equations with an efficient and high-order accurate pseudospectral method involving fast Fourier transform on an orthorhombic cell. A rich variety of structures for the phase separated brushes is predicted. Phase diagrams involving a series of system parameters, such as the aspect ratio of the nanorod, the grafting density, and the chain length are constructed. The results indicate that the phase structure of the mixed brush-rod system can be tailored by varying the grafted chain length and/or the aspect ratio of the rod to benefit the fabrication of polymeric nanocomposites.

Ma, Xin; Yang, Yingzi; Tang, Ping, E-mail: pingtang@fudan.edu.cn, E-mail: fengqiu@fudan.edu.cn; Qiu, Feng, E-mail: pingtang@fudan.edu.cn, E-mail: fengqiu@fudan.edu.cn [Department of Macromolecular Science, The State Key Laboratory of Molecular Engineering of Polymers, Key Laboratory of Computational Physical Sciences, Fudan University, Shanghai 200433 (China)] [Department of Macromolecular Science, The State Key Laboratory of Molecular Engineering of Polymers, Key Laboratory of Computational Physical Sciences, Fudan University, Shanghai 200433 (China); Zhu, Lei [Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106-7202 (United States)] [Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106-7202 (United States); Zhao, Bin [Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996 (United States)] [Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996 (United States)

2013-12-07

288

Preparation of metal adsorbent from poly(methyl acrylate)-grafted-cassava starch via gamma irradiation  

NASA Astrophysics Data System (ADS)

Metal adsorbent containing hydroxamic acid groups was successfully synthesized by radiation-induced graft copolymerization of methyl acrylate (MA) onto cassava starch. The optimum conditions for grafting were studied in terms of % degree of grafting (Dg). Conversion of the ester groups present in poly(methyl acrylate)-grafted-cassava starch copolymer into hydroxamic acid was carried out by treatment with hydroxylamine (HA) in the presence of alkaline solution. The maximum percentage conversion of the ester groups of the grafted copolymer, % Dg=191 (7.63 mmol/g of MA), into the hydroxamic groups was 70% (5.35 mmol/g of MA) at the optimum condition. The adsorbent of 191%Dg had total adsorption capacities of 2.6, 1.46, 1.36, 1.15 and 1.6 mmol/g-adsorbent for Cd2+, Al3+, UO22+, V5+ and Pb2+, respectively, in the batch mode adsorption.

Suwanmala, Phiriyatorn; Hemvichian, Kasinee; Hoshina, Hiroyuki; Srinuttrakul, Wannee; Seko, Noriaki

2012-08-01

289

Grafting of HEMA onto dopamine coated stainless steel by 60Co-? irradiation method  

NASA Astrophysics Data System (ADS)

A novel method for grafting of 2-hydroxyethyl methacrylate (HEMA) onto the surface of stainless steel (SS) was explored by using 60Co-? irradiation. The surface of SS was modified by coating of dopamine before radiation grafting. The grafting reaction was performed in a simultaneous irradiation condition. The chemical structures change of the surface before and after grafting was demonstrated by Fourier transform infrared (FTIR) spectrometer. The hydrophilicity of the samples was determined by water contact angle measurement in the comparison of the stainless steel in the conditions of pristine, dopamine coated and HEMA grafted. Surface morphology of the samples was characterized by atomic force microscope (AFM) and scanning electron microscope (SEM). The corrosion resistance properties of the samples were evaluated by Tafel polarization curve. The hemocompatibility of the samples were tested by platelet adhesion assay.

Jin, Wanqin; Yang, Liming; Yang, Wei; Chen, Bin; Chen, Jie

2014-12-01

290

Solid polymeric electrolytes obtained from modified natural polymers  

NASA Astrophysics Data System (ADS)

Polysaccharides like starch and cellulose derivatives, hydroxyethylcellulose (HEC) or hydroxypropylcellulose (HPC) were modified to obtain solid polymeric electrolytes. The chemical modifications were performed by the grafting of polymers with poly(ethylene oxide) mono and diisocyanates or JEFFAMINE (Shiff base). The physical modifications were made by the plasticization process of starch and cellulose derivatives with glycerol and ethylene glycol. All the samples obtained from polysaccharides were characterized by X-ray, thermal analysis (DSC) and impedance spectroscopy. The plasticized samples showed low glass transition temperatures (Tg); for HEC the value was about -60°C and for starch it was about -30°C. Tg values for grafted samples were of about -58°C for starch and -7°C for HPC. The low Tg values obtained are important to ensure good ionic conductivity that reached the values of about 10-5 Scm-1 for plasticized samples and 10-6 Scm-1 for grafted ones at room temperature. The good film forming and ionic conductivity properties of the samples of HEC, HPC and starch are very interesting candidates to be used as solid polymer electrolytes.

Pawlicka, Agnieszka; Machado, G. O.; Guimaraes, K. V.; Dragunski, Douglas C.

2003-10-01

291

ACL graft migration under cyclic loading  

Microsoft Academic Search

Elongation and migration of ACL grafts will lead to a deterioration of the initial stability of ACL reconstructions. The graft\\u000a migration has been sparsely investigated independently from the elongation of the graft–fixation complex. The hypothesis of\\u000a this investigation was that cyclic tensile loads cause a measurable migration of the grafts. Three graft\\/fixation combinations\\u000a were investigated in human femora (n = 7): human

Christian Staerke; Andreas Möhwald; Karl-Heinz Gröbel; Carsten Bochwitz; Roland Becker

2010-01-01

292

Saphenous vein graft vs. radial artery graft searching for the best second coronary artery bypass graft  

PubMed Central

Coronary artery bypass grafting (CABG) was first used in the late 1960s. This revolutionary procedure created hope among ischemic heart disease patients. Multiple conduits are used and the golden standard is the left internal mammary artery to the left anterior descending artery. Although all approaches were advocated by doctors, the use of saphenous vein grafts became the leading approach used by the majority of cardiac surgeons in the 1970s. The radial artery graft was introduced at the same time but was not as prevalent due to complications. It was reintroduced into clinical practice in 1989. The procedure was not well received initially but it has since shown superiority in patency as well as long-term survival after CABG. This review provides a summary of characteristics, technical features and patency rates of the radial artery graft in comparison with venous conduits. Current studies and research into radial artery grafts and saphenous vein grafts for CABG are explored. However, more studies are required to verify the various findings of the positive effects of coronary artery bypass grafting with the help of radial arteries on mortality and long-lasting patency. PMID:24198449

Al-Sabti, Hilal Ali; Al Kindi, Adil; Al-Rasadi, Khalid; Banerjee, Yajnavalka; Al-Hashmi, Khamis; Al-Hinai, Ali

2013-01-01

293

Brush/gold nanoparticle hybrids: effect of grafting density on the particle uptake and distribution within weak polyelectrolyte brushes.  

PubMed

The effect of the brush grafting density on the loading of 13 nm gold nanoparticles (AuNPs) into stimuli-responsive poly(N,N-(dimethylamino ethyl) methacrylate) (PDMAEMA) brushes anchored to flat impenetrable substrates is reported. Atom-transfer radical polymerization (ATRP) is used to grow polymer brushes via a "grafting from" approach from a 2-bromo-2-methyl-N-(3-(triethoxysilyl) propyl) propanamide (BTPAm)-covered silicon substrate. The grafting density is varied by using mixtures of initiator and a "dummy" molecule that is not able to initiate polymerization. A systematic study is carried out by varying the brush grafting density while keeping all of the other parameters constant. X-ray reflectivity is a suitable tool for investigating the spatial structure of the hybrid, and it is combined with scanning electron microscopy and UV/vis spectroscopy to study the particle loading and interpenetration of the particles within the polymer brush matrix. The particle uptake increases with decreasing grafting density and is highest for an intermediate grafting density because more space between the polymer chains is available. For very low grafting densities of PDMAEMA brushes, the particle uptake decreases because of a lack of the polymer matrix for the attachment of particles. The structure of the surface-grafted polymer chains changes after particle attachment. More water is incorporated into the brush matrix after particle immobilization, which leads to a swelling of the polymer chains in the hybrid material. Water can be removed from the brush by decreasing the relative humidity, which leads to brush shrinking and forces the AuNPs to get closer to each other. PMID:25275215

Christau, Stephanie; Möller, Tim; Yenice, Zuleyha; Genzer, Jan; von Klitzing, Regine

2014-11-01

294

Poly(vinylidene fluoride-co-hexafluoropropylene)-graft-poly(dopamine methacrylamide) copolymers: A nonlinear dielectric material for high energy density storage  

NASA Astrophysics Data System (ADS)

A nonlinear dielectric poly(vinylidene fluoride-co-hexafluoropropylene)-graft-poly(dopamine methacrylamide) [P(VDF-HFP)-g-PDMA] graft copolymer with ultra-high energy density of 33 J/cm3 was obtained by thermally initiated radical graft polymerization. It was observed that the dielectric constant of the graft copolymer films was 63% higher than that of P(VDF-HFP), with a large dielectric breakdown strength (>850 MV/m). Theoretical analyses and experimental measurements showed that the significant improvement in the electric polarization was attributed to the introduction of the highly polarizable hydroxyl groups in the PDMA side chains, and the large breakdown strength arose from the strong adhesion bonding of the catechol-containing graft copolymer to the metal electrode.

Rahimabady, Mojtaba; Qun Xu, Li; Arabnejad, Saeid; Yao, Kui; Lu, Li; Shim, Victor P. W.; Gee Neoh, Koon; Kang, En-Tang

2013-12-01

295

Interventions in Infrainguinal Bypass Grafts  

SciTech Connect

The interventional radiologist plays an important role in the detection and prevention of infrainguinal bypass failure. Early detection and evaluation of flow-limiting lesions effectively preserve graft (venous bypass and polyester or expanded polytetrafluoroethylene bypass) patency by identifying stenoses before occlusion occurs. Delay in treatment of the at-risk graft may result in graft failure and a reduced chance of successful revascularization. For this reason, surveillance protocols form an important part of follow-up after infrainguinal bypass surgery. As well as having an understanding of the application of imaging techniques including ultrasound, MR angiography, CT angiography and digital subtraction angiography, the interventional radiologist should have detailed knowledge of the minimally invasive therapeutic options. Percutaneous transluminal angioplasty (PTA), or alternatively cutting balloon angioplasty, is the interventional treatment of choice in prevention of graft failure and occlusion. Further alternatives include metallic stent placement, fibrinolysis, and mechanical thrombectomy. Primary assisted patency rates following PTA can be up to 65% at 5 years. When the endovascular approach is unsuccessful, these therapeutic options are complemented by surgical procedures including vein patch revision, jump grafting, or placement of a new graft.

Mueller-Huelsbeck, S., E-mail: muehue@rad.uni-kiel.de; Order, B.-M.; Jahnke, T. [University Hospital Schleswig-Holstein - Campus Kiel, Department of Radiology (Germany)

2006-02-15

296

Polymerization with freezing  

NASA Astrophysics Data System (ADS)

Irreversible aggregation processes involving reactive and frozen clusters are investigated using the rate equation approach. In aggregation events, two clusters join irreversibly to form a larger cluster; additionally, reactive clusters may spontaneously freeze. Frozen clusters do not participate in merger events. Generally, freezing controls the nature of the aggregation process, as demonstrated by the final distribution of frozen clusters. The cluster mass distribution has a power-law tail, Fk~k-?, when the freezing process is sufficiently slow. Different exponents, ? = 1 and 3, are found for the constant and the product aggregation rates, respectively. For the latter case, the standard polymerization model, either no gels, or a single gel, or even multiple gels, may be produced.

Ben-Naim, E.; Krapivsky, P. L.

2005-12-01

297

Switchable Adhesion from Bicomponent Polymeric Brushes  

NASA Astrophysics Data System (ADS)

We investigated the adhesive and wetting properties of bicomponent polymeric brushes made from end functionalized hydrophilic and hydrophobic polymer chains. The molecular organization of the mixed brush could be varied reversibly by exposure to selective solvents for the two polymers. Adhesive properties were tested by debonding a flat ended probe from soft pressure-sensitive-adhesives (hydrophobic & hydrophilic) and wetting properties were tested by contact angle measurements of water & diiodomethane droplets. The bicomponent brushes were chemically grafted on silicon wafers from end-functionalized chains. Wetting experiments were done directly on the wafers while for adhesion experiments, the wafers were glued on the flat end of the probe prior to the tests. In all cases the organization of the bicomponent brush could be modified reproducibly and reversibly by exposure to selective solvents. Following this strategy we succeeded to create remarkably stable adaptive polymer surfaces that can modify their adhesion and wetting reversibly and also tune them by varying the ratio of the bicomponent brush layer.

Retsos, Haris; Gorodyska, Ganna; Creton, Costantino

2005-03-01

298

Polymerization of glucans by enzymatically active membranes.  

PubMed

Conventional enzyme membrane reactors are not appropriate for a continuous synthesis of macromolecules and simultaneous product release. By immobilizing the enzyme in sufficiently large pores of a membrane an ensemble of miniaturized bioreactors is created. Product molecules are continuously removed from the enzyme by the flow of the reaction mixture across the membrane. Additionally, by varying the flow rate, it ought to be possible to influence the substrate as well as the enzyme-product residence times and thereby the product macromolecule's size. In this paper we present the first results of experiments involving enzymatic 1,4-alpha-glucan synthesis, using sucrose as substrate, maltooligosaccharides (DP 3-6) as primers, and membrane-immobilized amylosucrase. Epoxy groups for a covalent enzyme immobilization were generated on polypropylene microfiltration membranes by heterogeneous photoinitiated graft polymerization of glycidyl methacrylate. The influence of primer concentration and flow rate through the enzyme-membrane on amylosucrase activity, molecule growth, and coupling efficiency for glucose (% of coupled glucose versus free glucose) were investigated. The enzymatically mediated chain elongation of maltooligosaccharides by the successive addition of glucose units was achieved for the first time in a transmembrane process utilizing amylosucrase membranes. PMID:12363346

Becker, Margot; Provart, Nicholas; Lehmann, Ingeburg; Ulbricht, Mathias; Hicke, Hans-Georg

2002-01-01

299

Grafting titanium nitride surfaces with sodium styrene sulfonate thin films.  

PubMed

The importance of titanium nitride lies in its high hardness and its remarkable resistance to wear and corrosion, which has led to its use as a coating for the heads of hip prostheses, dental implants and dental surgery tools. However, the usefulness of titanium nitride coatings for biomedical applications could be significantly enhanced by modifying their surface with a bioactive polymer film. The main focus of the present work was to graft a bioactive poly(sodium styrene sulfonate) (pNaSS) thin film from titanium nitride surfaces via a two-step procedure: first modifying the surface with 3-methacryloxypropyltrimethoxysilane (MPS) and then grafting the pNaSS film from the MPS modified titanium through free radical polymerization. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used after each step to characterize success and completeness of each reaction. The surface region of the titanium nitride prior to MPS functionalization and NaSS grafting contained a mixture of titanium nitride, oxy-nitride, oxide species as well as adventitious surface contaminants. After MPS functionalization, Si was detected by XPS, and characteristic MPS fragments were detected by ToF-SIMS. After NaSS grafting, Na and S were detected by XPS and characteristic NaSS fragments were detected by ToF-SIMS. The XPS determined thicknesses of the MPS and NaSS overlayers were ?1.5 and ?1.7 nm, respectively. The pNaSS film density was estimated by the toluidine blue colorimetric assay to be 260?±?70 ng/cm(2). PMID:25280842

Zorn, Gilad; Migonney, Véronique; Castner, David G

2014-09-01

300

Radioimmunoassay of circulating schistosome antigen with a radiation-immobilized monoclonal antibody : Preliminary results  

NASA Astrophysics Data System (ADS)

A two-site immunoradiometric assay with a mouse monoclonal antibody to a circulating schistosome antigen was comparatively investigated using the monoclonal antibody either absorbed to microtiter plates (reference IRMA) or immobilized by several techniques. Radiation polymerization methods were carried out at Takasaki Radiation Chemistry Research Establishment, Takasaki, Gunma (I. Kaetsu, M. Kumakura), using 2-hydroxyethyl methacrylate monomers and 1 Mrad irradiation. A significant correlation was obtained with the reference IRMA and the assay using radiation polymerization-immobilized antibody ( r = 0.94), although non-specific binding to the polymer discs was higher (x 10) than with microtiter plates. Immobilization of the monoclonal antibody onto polypropylene/polyethylene copolymer films grafted with methacrylic acid irradiated at 0.68 Mrads and treated with carbodiimide/N-hydroxysuccinimide, was carried out at the Dept of Bioengineering, University of Washington, Seattle, Washington (A.S. Hoffman, W.R. Gombotz, S. Uenoyama). A significant correlation ( r = 0.90) was obtained with the reference IRMA. Non-specific binding was also higher than with microtiter plates (x 6). An important result was the increased shelf life of the immobilized reagent.

Dessaint, J. P.; Nogueira-Queiroz, J. A.; Capron, A.

301

Preparation of anion exchanger by amination of acrylic acid grafted polypropylene nonwoven fiber and its ion-exchange property.  

PubMed

To develop the polymeric adsorbent that possess anionic exchangeable function, PP-g-AA-Am fibers were prepared by photoinduced grafting of acrylic acid (AA) onto polypropylene (PP) nonwoven fibers and subsequent conversion of carboxyl group in grafted AA to an amine (Am) group by reaction with diethylene triamine (DETA). The amination of grafted AA increased with increase in the degree of grafting, the reaction time and temperature of the chemical modification process. Catalytic effect of metal chlorides such as AlCl(3) and FeCl(3) on the amination of grafted AA was significant but not essential to lead the amination. FT-IR and solid (13)C NMR data indicate that amine group was introduced into PP-g-AA fiber through amide linkage between grafted AA and DETA. The anion exchange capacity of PP-g-AA-Am fiber increased with increase in the degree of amination, but reached maximum value at about 60% amination of 150% grafted AA. PP-g-AA-Am fiber showed much higher maximum capacity for PO(4)-P and a similar capacity for NO(3)-N compared to commercial anion resins. Furthermore, the PP-g-AA-Am fiber also has adsorption ability for cations because of unaminated residual carboxyl group. PMID:16781723

Park, Hyun-Ju; Na, Choon-Ki

2006-09-01

302

High temperature structural, polymeric foams from high internal emulsion polymerization  

SciTech Connect

In 1982, a high internal phase emulsion (HIPE) polymerization process to manufacture microcellular, polymeric foam systems was patented by Unilever. This patent discloses a polymerization process that occurs in a water-in-oil emulsion in which the water represents at least 76% of the emulsion by volume. The oil phase consists of vinyl monomers such as styrene and acrylates that are crosslinked by divinyl monomers during polymerization. After polymerization and drying to remove the water phase, the result is a crosslinked polymer foam with an open cell microstructure that is homogeneous throughout in terms of morphology, density, and mechanical properties. Since 1982, numerous patents have examined various HIPE polymerized foam processing techniques and applications that include absorbents for body fluids, cleaning materials, and ion exchange systems. All the published HIPE polymerized foams have concentrated on materials for low temperature applications. Copolymerization of styrene with maleic anhydride and N-substituted maleimides to produce heat resistant thermoplastics has been studied extensively. These investigations have shown that styrene will free radically copolymerize with N-substituted maleimides to create an alternating thermoplastic copolymer with a Tg of approximately 200{degrees}C. However, there are many difficulties in attempting the maleimide styrene copolymerization in a HIPE such as lower polymerization temperatures, maleimide solubility difficulties in both styrene and water, and difficulty obtaining a stable HIPE with a styrene/maleimide oil phase. This work describes the preparation of copolymer foams from N-ethylmaleimide and Bis(3-ethyl-5-methyl-4-maleimide-phenyl)methane with styrene based monomers and crosslinking agents.

Hoisington, M.A.; Duke, J.R.; Apen, P.G.

1996-02-01

303

Craniofacial Bone Grafting: Wolff's Law Revisited  

PubMed Central

Bone grafts are used for the reconstruction of congenital and acquired deformities of the facial skeleton and, as such, comprise a vital component of the craniofacial surgeon's armamentarium. A thorough understanding of bone graft physiology and the factors that affect graft behavior is therefore essential in developing a more intelligent use of bone grafts in clinical practice. This article presents a review of the basic physiology of bone grafting along with a survey of pertinent concepts and current research. The factors responsible for bone graft survival are emphasized. PMID:22110789

Oppenheimer, Adam J.; Tong, Lawrence; Buchman, Steven R.

2008-01-01

304

Bone graft substitute: allograft and xenograft.  

PubMed

Rapid bone graft incorporation for structural rigidity is essential. Early range of motion, exercise, and weight-bearing are keys to rehabilitation. Structural and nonstructural bone grafts add length, height, and volume to alter alignment, function, and appearance. Bone graft types include: corticocancellous autograft, allograft, xenograft, and synthetic graft. Autogenic grafts are harvested from the patient, less likely to be rejected, and more likely to be incorporated; however, harvesting adds a procedure and donor site complication is common. Allografts, xenografts, and synthetic grafts eliminate secondary procedures and donor site complications; however, rejection and slower incorporation can occur. PMID:25440415

Shibuya, Naohiro; Jupiter, Daniel C

2015-01-01

305

Polymeric micelles as new drug carriers  

Microsoft Academic Search

Advances in block copolymer syntheses have led to polymeric micelles that may serve as nanoscopic drug carriers. For drug delivery, micelles were prepared from biocompatible and biodegradable block copolymers. The polymeric micelles display functional groups on their surfaces for attachment of pilot molecules. Researchers are establishing chemical as well as physical routes of loading drugs into polymeric micelles. Notably, polymeric

Glen S. Kwon; Teruo Okano

1996-01-01

306

Organometallic Polymeric Conductors  

NASA Technical Reports Server (NTRS)

For aerospace applications, the use of polymers can result in tremendous weight savings over metals. Suitable polymeric materials for some applications like EMI shielding, spacecraft grounding, and charge dissipation must combine high electrical conductivity with long-term environmental stability, good processability, and good mechanical properties. Recently, other investigators have reported hybrid films made from an electrically conductive polymer combined with insulating polymers. In all of these instances, the films were prepared by infiltrating an insulating polymer with a precursor for a conductive polymer (either polypyrrole or polythiophene), and oxidatively polymerizing the precursor in situ. The resulting composite films have good electrical conductivity, while overcoming the brittleness inherent in most conductive polymers. Many aerospace applications require a combination of properties. Thus, hybrid films made from polyimides or other engineering resins are of primary interest, but only if conductivities on the same order as those obtained with a polystyrene base could be obtained. Hence, a series of experiments was performed to optimize the conductivity of polyimide-based composite films. The polyimide base chosen for this study was Kapton. 3-MethylThiophene (3MT) was used for the conductive phase. Three processing variables were identified for producing these composite films, namely time, temperature, and oxidant concentration for the in situ oxidation. Statistically designed experiments were used to examine the effects of these variables and synergistic/interactive effects among variables on the electrical conductivity and mechanical strength of the films. Multiple linear regression analysis of the tensile data revealed that temperature and time have the greatest effect on maximum stress. The response surface of maximum stress vs. temperature and time (for oxidant concentration at 1.2 M) is shown. Conductivity of the composite films was measured for over 150 days in air at ambient temperature. The conductivity of the films dropped only half an order of magnitude in that time. Films aged under vacuum at ambient temperature diminished slightly in conductivity in the first day, but did not change thereafter. An experimental design approach will be applied to maximize the efficiency of the laboratory effort. The material properties (initial and long term) will also be monitored and assessed. The experimental results will add to the existing database for electrically conductive polymer materials. Attachments: 1) Synthesis Crystal Structure, and Polymerization of 1,2:5,6:9,10-Tribenzo-3,7,11,13-tetradehydro(14) annulene. 2) Reinvestigation of the Photocyclization of 1,4-Phenylene Bis(phenylmaleic anhydride): Preparation and Structure of (5)Helicene 5,6:9,10-Dianhydride. 3) Preparation and Structure Charecterization of a Platinum Catecholate Complex Containing Two 3-Ethynyltheophone Groups. and 4) Rigid-Rod Polymers Based on Noncoplanar 4,4'-Biphenyldiamines: A Review of Polymer Properties vs Configuration of Diamines.

Youngs, Wiley J.

1997-01-01

307

Evidence for vertical phase separation in densely grafted, high-molecular-weight poly( N -isopropylacrylamide) brushes in water  

NASA Astrophysics Data System (ADS)

The detailed conformational change of poly( N -isopropylacrylamide) (PNIPAM) brushes at high grafting density in D2O was investigated as a function of temperature using neutron reflection. PNIPAM chains were grafted at high surface density from gold and silicon oxide surfaces by atom transfer radical polymerization. Whereas single layer profiles were observed for temperatures below and above the transition region, bilayer profiles were observed for a narrow range of temperatures near the transition. This nonmonotonic change in the concentration profile with temperature is discussed in the context of theoretical models of vertical phase separation within a brush.

Yim, H.; Kent, M. S.; Satija, S.; Mendez, S.; Balamurugan, S. S.; Balamurugan, S.; Lopez, G. P.

2005-11-01

308

Polymerization of anionic wormlike micelles.  

PubMed

Polymerizable anionic wormlike micelles are obtained upon mixing the hydrotropic salt p-toluidine hydrochloride (PTHC) with the reactive anionic surfactant sodium 4-(8-methacryloyloxyoctyl)oxybenzene sulfonate (MOBS). Polymerization captures the cross-sectional radius of the micelles (approximately 2 nm), induces micellar growth, and leads to the formation of a stable single-phase dispersion of wormlike micellar polymers. The unpolymerized and polymerized micelles were characterized using static and dynamic laser light scattering, small-angle neutron scattering, 1H NMR, and stopped-flow light scattering. Stopped-flow light scattering was also used to measure the average lifetime of the unpolymerized wormlike micelles. A comparison of the average lifetime of unpolymerized wormlike micelles with the surfactant monomer propagation rate was used to elucidate the mechanism of polymerization. There is a significant correlation between the ratio of the average lifetime to the monomer propagation rate and the average aggregation number of the polymerized wormlike micelles. PMID:16430253

Zhu, Zhiyuan; González, Yamaira I; Xu, Hangxun; Kaler, Eric W; Liu, Shiyong

2006-01-31

309

Endocytosis of PEGylated nanoparticles accompanied by structural and free energy changes of the grafted polyethylene glycol.  

PubMed

Nanoparticles (NPs) are in use to efficiently deliver drug molecules into diseased cells. The surfaces of NPs are usually grafted with polyethylene glycol (PEG) polymers, during so-called PEGylation, to improve water solubility, avoid aggregation, and prevent opsonization during blood circulation. The interplay between grafting density ?p and grafted PEG polymerization degree N makes cellular uptake of PEGylated NPs distinct from that of bare NPs. To understand the role played by grafted PEG polymers, we study the endocytosis of 8 nm sized PEGylated NPs with different ?p and N through large scale dissipative particle dynamics (DPD) simulations. The free energy change Fpolymer of grafted PEG polymers, before and after endocytosis, is identified to have an effect which is comparable to, or even larger than, the bending energy of the membrane during endocytosis. Based on self-consistent field theory Fpolymer is found to be dependent on both ?p and N. By incorporating Fpolymer, the critical ligand-receptor binding strength for PEGylated NPs to be internalized can be correctly predicted by a simple analytical equation. Without considering Fpolymer, it turns out impossible to predict whether the PEGylated NPs will be delivered into the diseased cells. These simulation results and theoretical analysis not only provide new insights into the endocytosis process of PEGylated NPs, but also shed light on the underlying physical mechanisms, which can be utilized for designing efficient PEGylated NP-based therapeutic carriers with improved cellular targeting and uptake. PMID:25002266

Li, Ying; Kröger, Martin; Liu, Wing Kam

2014-10-01

310

Polyester-grafted cellulose nanowhiskers: a new approach for tuning the microstructure of immiscible polyester blends.  

PubMed

Cellulose nanowhiskers (CNW), extracted from ramie fibers by sulfuric acid hydrolysis, were used as substrates to compatibilize binary polyester blends containing 50/50 (w/w) polycaprolactone (PCL) and polylactide (PLA). To tailor their interfacial energy and fine-tune their adhesion with the components of the blend, CNW were subjected to different surface polyester grafting by the means of ring-opening polymerization. PCL and PLA homopolyesters as well as P(CL-b-LA) diblock copolymers were successfully grafted on the surface of CNW and the resulting substrates were loaded into the PCL/PLA blend by melt-blending. Morphological and rheological analyses were conducted in order to evaluate the ability of these nanoparticles to enhance the compatibility of PCL/PLA blends. Our results showed that unmodified CNW as well as (co)polyester-grafted CNW improved, at different levels, the compatibility of PCL/PLA blends by preventing from coalescence the dispersed domains. (co)polyester-grafted CNW also enhance the mechanical properties of the blend, which can be explained by the formation of cocontinuous phase morphology at the interface. Our findings suggest that (co)polyester-grafted CNW, especially CNW-g-P(CL-b-LA) diblock copolymers, can serve as a suitable nanofiller to tune the compatibility of PCL/PLA blends and their related microstructures. PMID:22738142

Goffin, Anne-Lise; Habibi, Youssef; Raquez, Jean-Marie; Dubois, Philippe

2012-07-25

311

Grafting of gallic acid onto chitosan enhances antioxidant activities and alters rheological properties of the copolymer.  

PubMed

A new, simple, and effective method to graft gallic acid (GA) onto chitosan (CS) in aqueous solution in the presence of carbodiimide and hydroxybenzotriazole was developed. The grafting amount of GA reached as much as 209.9 mg/g of copolymer, which appears as the highest one among the reported literature, and the grafting degree of GA to CS was adjustable with modulation of the mass ratio of GA to CS. The covalent insertion of GA onto the polymeric backbones was confirmed by UV-vis and (1)H NMR analyses. Grafting endowed the resulting copolymer GA-grafted-CS (GA-g-CS) with both the advantages of CS and GA. The antioxidant capacity of GA-g-CS was much higher than that of the plain CS examined by assays of DPPH, superoxide, and ABTS radicals scavenging activities, reducing power, chelating power, inhibition of lipid peroxidation, ferric reducing antioxidant potential, and ?-carotene-linoleic acid assays. Particularly, GA-g-CS showed significantly higher antioxidant activity than GA in ?-carotene-linoleic acid assay. Furthermore, the viscosity of GA-g-CS was significantly higher than that of CS. The present study developed a novel approach to synthesize GA-g-CS that could be a potential biomaterial in food industries. PMID:25198516

Xie, Minhao; Hu, Bing; Wang, Yan; Zeng, Xiaoxiong

2014-09-17

312

Plant grafting: new mechanisms, evolutionary implications  

PubMed Central

Grafting, an old plant propagation practice, is still widely used with fruit trees and in recent decades also with vegetables. Taxonomic proximity is a general prerequisite for successful graft-take and long-term survival of the grafted, composite plant. However, the mechanisms underlying interspecific graft incompatibility are as yet insufficiently understood. Hormonal signals, auxin in particular, are believed to play an important role in the wound healing and vascular regeneration within the graft union zone. Incomplete and convoluted vascular connections impede the vital upward and downward whole plant transfer routes. Long-distance protein, mRNA and small RNA graft-transmissible signals currently emerge as novel mechanisms which regulate nutritional and developmental root/top relations and may play a pivotal role in grafting physiology. Grafting also has significant pathogenic projections. On one hand, stock to scion mechanical contact enables the spread of diseases, even without a complete graft union. But, on the other hand, grafting onto resistant rootstocks serves as a principal tool in the management of fruit tree plagues and vegetable soil-borne diseases. The ‘graft hybrid’ historic controversy has not yet been resolved. Recent evidence suggests that epigenetic modification of DNA-methylation patterns may account for certain graft-transformation phenomena. Root grafting is a wide spread natural phenomenon; both intraspecific and interspecific root grafts have been recorded. Root grafts have an evolutionary role in the survival of storm-hit forest stands as well as in the spread of devastating diseases. A more fundamental evolutionary role is hinted by recent findings that demonstrate plastid and nuclear genome transfer between distinct Nicotiana species in the graft union zone, within a tissue culture system. This has led to the formation of alloploid cells that, under laboratory conditions, gave rise to a novel, alloploid Nicotiana species, indicating that natural grafts may play a role in plant speciation, under certain circumstances. PMID:25566298

Goldschmidt, Eliezer E.

2014-01-01

313

Impaction grafting of the acetabulum with ceramic bone graft substitute  

PubMed Central

Background and purpose Loss of bone stock remains a challenge in revision hip surgery. Grafting with allograft is well established, but there are problems with availability, cost, infection, antigenicity, reproducibility, and stability of the created construct. BoneSave is a biphasic porous ceramic consisting of sintered 80% tricalcium phosphate and 20% hydroxyapatite. In vitro and in vivo studies, including its use mixed with allograft, have shown good results in impaction grafting. This is the first reported series of its use alone in impaction grafting of the acetabulum. Methods Methods We conducted a retrospective review of a cohort of 43 consecutive patients undergoing impaction grafting of contained acetabular defects by multiple surgeons at a single centre. All patients received uncemented acetabular components. They were followed up radiographically, together with self-reported satisfaction scale (SAPS), Oxford hip score (OHS), and Short-Form 12 (SF12) health survey. Kaplan-Meier survivorship analysis was performed with revision of the acetabular component, revision of any part of the construct, and reoperation as endpoints. Results The fate of all cases was known. Mean follow-up was 4 years. 5 patients died during follow-up, with their constructs in situ. The survivorship of the acetabular component was 98% (95% CI: 85–100) at 7 years. 1 acetabular component was revised for infection and there was 1 radiographic acetabular failure. The median OHS was 36 (6–48), the median SF12 PCS was 36 (14–57), the median SAPS was 75 (0–100), and the median SF12 MCS was 50 (23–64). The graft material had incorporated in all 3 zones of the acetabulum in 33 out of 37 cases with complete radiographic follow-up. Interpretation Medium-term results show that BoneSave alone is a reliable material for impaction grafting of contained defects in the acetabulum at revision surgery. PMID:23992140

Dacombe, Peter J; Webb, Jason C J; Blom, Ashley W

2013-01-01

314

Polymeric phospholipids as new biomaterials.  

PubMed

Phospholipid polymers form a new class of biomaterials with many potential applications in medicine and research. The development of these compounds is based upon the mimicry of cell surfaces and reflects our current understanding of the properties of membrane lipids. Physicochemical characterization of the monomeric, diacetylenic phospholipids illustrates the similarities to naturally occurring lipids, similarities that are confirmed by the capacity to enrich the membranes of A. laidlawii to the level of 90% diacetylenic lipid. Polymerization of diacetylenic phospholipids is easily attained by irradiation and produces a stable, crystalline array. The ability to link membrane lipids covalently permits the isothermal restriction in their motion, and is useful in basic studies of biomembranes. The thromboresistance of polymeric phosphatidylcholines in vitro may be a consequence of the inability of phosphatidylcholines to participate in coagulation. The restricted lateral diffusion of proteins along a polymeric lattice will also inhibit the formation of coagulation complexes. Existing polymers may be altered by a coating of polymeric lipid obtained by the Langmuir-Blodgett method. Polymerized vesicles display significant reductions in permeability and aggregation. Entrapment of soluble materials and reconstitution of membrane proteins may be exploited in controlled and site-directed drug delivery. Polymerization of cells in situ produces "cellular capsules" with entrapped membrane and cellular components. Polymeric hemosomes are capable of gas transport and may function as red cell surrogates. The hybrid qualities of biomembranes (polar surfaces, nonthrombogenic, low antigenic potential, and low permeability) and synthetic polymers (chemical and physical stability) suggest that polymeric phosphatidylcholines may serve as models for biomaterials design. PMID:3860157

Hayward, J A; Johnston, D S; Chapman, D

1985-01-01

315

Kinetics of silica polymerization  

SciTech Connect

The polymerization of silicic acid in geothermal brine-like aqueous solutions to produce amorphous silica in colloidal form has been studied experimentally and theoretically. A large amount of high quality experimental data has been generated over the temperature rang 23 to 100{sup 0}C. Wide ranges of dissolved silica concentration, pH, and sodium chloride concentration were covered. The catalytic effects of fluoride and the reaction inhibiting effects of aluminum and boron were studied also. Two basic processes have been separately studied: the formation of new colloidal particles by the homogeneous nucleation process and the deposition of dissolved silica on pre-existing colloidal particles. A rigorous theory of the formation of colloidal particles of amorphous silica by homogeneous nucleation was developed. This theory employs the Lothe-Pound formalism, and is embodied in the computer code SILNUC which quantitatively models the homogeneous nucleation and growth of colloidal silica particles in more than enough detail for practical application. The theory and code were extensively used in planning the experimental work and analyzing the data produced. The code is now complete and running in its final form. It is capable of reproducing most of the experimental results to within experimental error. It is also capable of extrapolation to experimentally inaccessible conditions, i.e., high temperatures, rapidly varying temperature and pH, etc.

Weres, O.; Yee, A.; Tsao, L.

1980-05-01

316

Gels from soft hairy nanoparticles in polymeric matrices  

NASA Astrophysics Data System (ADS)

Hairy particles represent a huge class of soft colloids with tunable interactions and properties. Advances in synthetic chemistry have enabled obtaining well-characterized such systems for specific needs. In this talk we present two model hairy soft particles with diameters of the order of tens of nanometers, star polymers and polymerically grafted spherical particles. In particular, we discuss design strategies for dispersing them in polymeric matrices and eventually creating and breaking gels. Control parameters are the matrix molar mass, the grafting density (or functionality) and the size of the grafts (or arms). The linear viscoelastic properties and slow time evolution of the gels are examined in view of the existing knowledge from colloidal gels consisting of micron-sized particles, and compared. In the case of stars we start from a concentrated glassy suspension in molecular solvent and add homopolymer at increasing concentration, and as a result of the induced osmotic pressure the stars shrink and a depletion gel is formed. For the grafted colloidal particles, they are added at low concentration to a polymer matrix, and it has been shown that under certain conditions the anisotropy of interactions gives rise to network formation. We then focus on the nonlinear rheological response and in particular the effect of shear flow in inducing a solid to liquid transition. Our studies show that the yielding process is gradual and shares many common features with that of flocculated colloidal suspensions, irrespectively of the shape of the building block of the gel. Whereas shear can melt such a gel, it cannot break it into its constituent blocks and hence fully disperse the hairy nanoparticles. On the other hand, the hairy particles are intrinsically hybrid. We show how this important feature is reflected on the heating of the gels. In that case, the mismatch of thermal expansion coefficients of core and shell appears to play a role on the particle response as it imposes and internal strain on the particle, which in turn changes the shell conformation and under some conditions can lead to thermal melting of the gel. These alternative avenues for manipulating the gel-to-liquid transition have potential implications in directing the properties of hairy nanoparticles and their assemblies in viscoelastic matrices. Parts of this work reflect collaboration with D. Truzzolillo (FORTH), J. F. Moll and S. K.Kumar (Columbia). R. H. Colby (Penn State), M. Gauthier (Waterloo) and B. C. Benicewicz (Univ. South Carolina).

Vlassopoulos, Dimitris

2013-03-01

317

Kinetics of the formation and structure of oligoperoxide nanolayers and grafted polymer brushes on glass plate surface  

NASA Astrophysics Data System (ADS)

Functional oligoperoxide surfactants and coordinating oligoperoxide metal complexes were studied as modifiers of glass flat plates to provide the localization of radical forming sites and other functional fragments in adsorbed polymeric layers of a nanoscale thickness. Both the kinetics of the coating formation and properties of the nanolayers witness the dependence of the packing density of oligoperoxide molecules in the coatings on the oligoperoxide natures, concentrations and conditions of the sorption modification. The availability of definite amount of peroxide groups in formed nanolayer provides the possibility of controlled radical graft polymerization initiated from modified surface leading to reliable surface protection, functionality and targeted surface hydrophilic-hydrophobic properties.

Kostruba, Andriy; Zaichenko, Alexander; Mitina, Natalya; Rayevska, Kateryna; Hertsyk, Kateryna

2008-09-01

318

Types of Coronary Artery Bypass Grafting  

MedlinePLUS

... shocks are used to restart the heart. Off-Pump Coronary Artery Bypass Grafting This type of CABG ... heart-lung bypass machine isn't used. Off-pump CABG sometimes is called beating heart bypass grafting. ...

319

POST CORONARY ARTERY BYPASS GRAFT STUDY (CABG)  

EPA Science Inventory

Relative effectiveness of moderate versus more aggressive lipid lowering, and of low dose anticoagulation versus placebo, in delaying saphenous vein coronary bypass graft atherosclerosis and preventing occlusion of saphenous grafts of patients with saphenous vein coronary bypass ...

320

Recanalization of an Occluded Infrainguinal Vein Graft Complicated by Graft Aneurysm  

SciTech Connect

The technique of subintimal angioplasty has been described for the recanalisation of native vessels after occlusion of infrainguinal vascular bypass grafts. We report a case in which an attempt at such treatment resulted in inadvertent but successful recanalisation of the occluded vein graft instead. This was complicated by graft perforation and subsequent graft aneurysm which was successfully treated with a covered stent.

Kakani, Nirmal; Travis, Simon; Hancock, John [Royal Cornwall Hospital, Department of Clinical Imaging (United Kingdom)], E-mail: John.Hancock@rcht.cornwall.nhs.uk

2007-11-15

321

The consequences of a failed femoropopliteal bypass grafting: Comparison of saphenous vein and PTFE grafts  

Microsoft Academic Search

Objectives: Although there are numerous reports comparing saphenous vein (SV) and polytetrafluoroethylene (PTFE) with respect to the patency rates for femoropopliteal bypass grafts, the clinical consequences of failed grafts are not as well described. This study compares the outcomes of failed SV and PTFE grafts with a specific emphasis on the degree of acute limb ischemia caused by graft occlusion.

Mark R. Jackson; Todd P. Belott; Timothy Dickason; William J. Kaiser; J. Gregory Modrall; R. James Valentine; G. Patrick Clagett

2000-01-01

322

Self-assembled polymeric micelles based on hyaluronic acid-g-poly(D,L-lactide-co-glycolide) copolymer for tumor targeting.  

PubMed

Graft copolymer composed hyaluronic acid (HA) and poly(D,L-lactide-co-glycolide) (PLGA) (HAgLG) was synthesized for antitumor targeting via CD44 receptor of tumor cells. The carboxylic end of PLGA was conjugated with hexamethylenediamine (HMDA) to have amine end group in the end of chain (PLGA-amine). PLGA-amine was coupled with carboxylic acid of HA. Self-assembled polymeric micelles of HAgLG have spherical morphologies and their sizes were around 50-200 nm. Doxorubicin (DOX)-incorporated polymeric micelles were prepared by dialysis procedure. DOX was released over 4 days and its release rate was accelerated by the tumoric enzyme hyaluronidase. To assess targetability of polymeric micelles, CD44-positive HepG2 cells were employed treated with fluorescein isothiocyanate (FITC)-labeled polymeric micelles. HepG2 cells strongly expressed green fluorescence at the cell membrane and cytosol. However, internalization of polymeric micelles were significantly decreased when free HA was pretreated to block the CD44 receptor. Furthermore, the CD44-specific anticancer activity of HAgLG polymeric micelles was confirmed using CD44-negative CT26 cells and CD44-positive HepG2 cells. These results indicated that polymeric micelles of HaLG polymeric micelles have targetability against CD44 receptor of tumor cells. We suggest HAgLG polymeric micelles as a promising candidate for specific drug targeting. PMID:25216338

Son, Gyung Mo; Kim, Hyun Yul; Ryu, Je Ho; Chu, Chong Woo; Kang, Dae Hwan; Park, Su Bum; Jeong, Young-Il

2014-01-01

323

Self-Assembled Polymeric Micelles Based on Hyaluronic Acid-g-Poly(d,l-lactide-co-glycolide) Copolymer for Tumor Targeting  

PubMed Central

Graft copolymer composed hyaluronic acid (HA) and poly(d,l-lactide-co-glycolide) (PLGA) (HAgLG) was synthesized for antitumor targeting via CD44 receptor of tumor cells. The carboxylic end of PLGA was conjugated with hexamethylenediamine (HMDA) to have amine end group in the end of chain (PLGA-amine). PLGA-amine was coupled with carboxylic acid of HA. Self-assembled polymeric micelles of HAgLG have spherical morphologies and their sizes were around 50–200 nm. Doxorubicin (DOX)-incorporated polymeric micelles were prepared by dialysis procedure. DOX was released over 4 days and its release rate was accelerated by the tumoric enzyme hyaluronidase. To assess targetability of polymeric micelles, CD44-positive HepG2 cells were employed treated with fluorescein isothiocyanate (FITC)-labeled polymeric micelles. HepG2 cells strongly expressed green fluorescence at the cell membrane and cytosol. However, internalization of polymeric micelles were significantly decreased when free HA was pretreated to block the CD44 receptor. Furthermore, the CD44-specific anticancer activity of HAgLG polymeric micelles was confirmed using CD44-negative CT26 cells and CD44-positive HepG2 cells. These results indicated that polymeric micelles of HaLG polymeric micelles have targetability against CD44 receptor of tumor cells. We suggest HAgLG polymeric micelles as a promising candidate for specific drug targeting. PMID:25216338

Son, Gyung Mo; Kim, Hyun Yul; Ryu, Je Ho; Chu, Chong Woo; Kang, Dae Hwan; Park, Su Bum; Jeong, Young-IL

2014-01-01

324

Bone grafting in shoulder arthroplasty.  

PubMed

Shoulder arthroplasty is one of the fastest-growing fields in orthopedic surgery. Deficiency of the glenoid or humeral bone stock is a major challenge that can result from degenerative arthritis, component loosening or extraction, fracture, or malignancy. Approximately 15% of primary reconstructions will require bone grafting, and the rate is higher for revisions. The authors present a systematic review of the current literature focused on the indications for and results of bone grafting techniques. This provides the practicing surgeon with a set of strategies to address bone loss in the primary and revision settings, whether using an anatomic or reverse design. PMID:23127445

Riboh, Jonathan C; Garrigues, Grant E

2012-11-01

325

Graft inserter for anterior cervical fusion.  

PubMed

The authors have developed a simple instrument for graft insertion in anterior cervical fusion. This device obviates the need for screw distraction of the adjacent vertebrae or the use of an impactor for insertion. This device simplifies graft insertion where the disc space is narrow, particularly in multilevel fusions, and reduces the risk of over-penetration of the graft. PMID:24974192

Hitchon, Patrick W; Kumar, Rajinder; Viljoen, Stephanus; Dahdaleh, Nader S

2014-11-01

326

Functional Grafts of the Anterior Pituitary Gland  

Microsoft Academic Search

A study has been made of pituitary grafts placed into hypophysectomized adult rats under the median eminence of the tuber cinereum, under the temporal lobe of the brain and into the hypophysial capsule. Good union was obtained in all three sites, the grafts becoming richly vascularized and remaining viable for long periods. Grafts placed under the median eminence acquired vascular

G. W. Harris; Dora Jacobsohn

1952-01-01

327

Polymeric materials for neovascularization  

NASA Astrophysics Data System (ADS)

Revascularization therapies have emerged as a promising strategy to treat various acute and chronic wounds, cardiovascular diseases, and tissue defects. It is common to either administer proangiogenic growth factors, such as vascular endothelial growth factor (VEGF), or transplant cells that endogenously express multiple proangiogenic factors. Additionally, these strategies utilize a wide variety of polymeric systems, including hydrogels and biodegradable plastics, to deliver proangiogenic factors in a sophisticated manner to maintain a sustained proangiogenic environment. Despite some impressive results in rebuilding vascular networks, it is still a challenging task to engineer mature and functional neovessels in target tissues, because of the increasing complexities involved with neovascularization applications. To resolve these challenges, this work aims to design a wide variety of proangiogenic biomaterial systems with tunable properties used for neovascularization therapies. This thesis describes the design of several biomaterial systems used for the delivery of proangiogenic factors in neovascularization therapies, including: an electrospun/electrosprayed biodegradable plastic patch used for directional blood vessel growth (Chapter 2), an alginate-g-pyrrole hydrogel system that biochemically stimulates cellular endogenous proangiogenic factor expression (Chapter 3), an enzyme-catalyzed alginate-g-pyrrole hydrogel system for VEGF delivery (Chapter 4), an enzyme-activated alginate-g-pyrrole hydrogel system with systematically controllable electrical and mechanical properties (Chapter 5), and an alginate-g-pyrrole hydrogel that enables the decoupled control of electrical conductivity and mechanical rigidity and is use to electrically stimulate cellular endogenous proangiogenic factor expression (Chapter 6). Overall, the biomaterial systems developed in this thesis will be broadly useful for improving the quality of a wide array of molecular and cellular based revascularization therapies.

DeVolder, Ross John

328

Polymer grafting surface as templates for the site-selective metallization  

NASA Astrophysics Data System (ADS)

We report a simple, low-cost and universal method for the fabrication of copper circuit patterns on a wide range of flexible polymeric substrates. This method relies on procedures to modify the polymeric substrates with grafted polymer template to form surface-bound N-containing groups, which can bind palladium catalysts that subsequently initiate the site-selective deposition of copper granular layer patterns. The fabrications of patterned copper films were demonstrated on three kinds of flexible polymeric films including poly(imide) (PI), poly(ethylene naphthalate) (PEN) and poly(ethylene terephthalate) (PET) with minimum feature sizes of 200 ?m. The films were characterized by ATR FT-IR, contact angle, XPS, XRD, TEM, SEM. Furthermore, the copper layered structure shows good adhesion with polymeric film. This method, which provides a promising strategy for the fabrication of copper circuit patterns on flexible polymeric substrates, has the potential in manufacturing conductive features adopted in various fields including modern electronics, opto-electronics and photovoltaic applications.

Yang, Fang; Li, Peiyuan; Li, Xiangcheng; Huo, Lini; Chen, Jinhao; Chen, Rui; Na, Wei; Tang, Wanning; Liang, Lifang; Su, Wei

2013-06-01

329

Aqueous-based initiator attachment and ATRP grafting of polymer brushes from poly(methyl methacrylate) substrates.  

PubMed

Many polymers, such as PMMA, are very susceptible to swelling or dissolution by organic solvents. Growing covalently attached polymer brushes from these surfaces by atom-transfer radical polymerization (ATRP) is challenging because of the typical requirement of organic solvent for initiator immobilization. We report an unprecedented, aqueous-based route to graft poly(N-isopropylacrylamide), PNIPAAm, from poly(methyl methacrylate), PMMA, surfaces by ATRP, wherein the underlying PMMA is unaffected. Successful attachment of the ATRP initiator, N-hydroxysuccinimidyl-2-bromo-2-methylpropionate, on amine-bearing PMMA surfaces was confirmed by XPS. From this surface-immobilized initiator, thermoresponsive PNIPAAm brushes were grown by aqueous ATRP to yield optically transparent PNIPAAm-grafted PMMA surfaces. This procedure is valuable, as it can be applied for the aqueous-based covalent attachment of ATRP initiator on any amine-functionalized surface, with subsequent polymerization of a variety of monomers. PMID:22967226

Balamurugan, Sreelatha S; Subramanian, Balamurugan; Bolivar, Jowell G; McCarley, Robin L

2012-10-01

330

Vascularization of the area between free grafts and irradiated graft beds in the neck in rats.  

PubMed

Inflammatory lesions of the vascular endothelium after preoperative radiotherapy often cause healing-delayed healing of free flaps in the irradiated graft bed. We investigated changes in neovascularization in the transition area between grafted tissues and irradiated tissues of the graft bed. We irradiated the neck(30 and 50 Gy total dose) in 102 Wistar rats and then grafted a free myocutaneous gracilis flap to the irradiated region of the neck 4 weeks later. We examined histologically the tissues of the graft, the transition area between the graft and the irradiated graft bed, and the graft bed. In contrast to control rats, the tissues in the irradiated animals showed a qualitatively reduced and a more irregular capillary distribution, with substantial fibrosis in the irradiated graft bed. We also found significant differences in vascularization and mean capillary lumen in the transitional zone between graft and graft bed in the irradiated rats compared with controls (P = 0.004 and P < 0.001, respectively). Both number and diameter of capillaries were reduced in the irradiated graft bed tissue. The graft failed to improve vascularization in the transitional zone between graft and irradiated tissue, so we conclude that it is the vascularization status of the bed tissue rather than that of the transplant tissue that is the limiting factor for graft healing. PMID:11883968

Schultze-Mosgau, S; Rödel, F; Radespiel-Tröger, M; Wörl, J; Grabenbauer, G G; Neukam, F W

2002-02-01

331

Grafting Strategy to Develop Single Site Titanium on an Amorphous Silica Surface  

SciTech Connect

Titanium/silica systems were prepared by grafting a titanium alkoxide (titanium isopropoxide and titanium (triethanolaminate) isopropoxide) precursor onto amorphous silica. The grafting process, which consisted of the hydrolysis of the Ti precursor by the hydroxyl groups on the silica surface, yielded samples containing Ti-loadings of 1-1.6 wt %. The as synthesized and calcined TiO2-SiO2 samples were characterized by UV-vis, FTIR, XPS, and XANES spectroscopic techniques. These systems were tested in the liquid-phase epoxidation of oct-1-ene with hydrogen peroxide reaction. Spectroscopic data indicated that titanium anchoring takes place by reaction between the alkoxide precursor and surface OH groups of the silica substrate. The nature of surface titanium species generated by chemical grafting depends largely on the titanium precursor employed. Thus, the titanium isopropoxide precursor yields tetrahedrally coordinated polymeric titanium species, which give rise to a low-efficiency catalyst. However, if an atrane precursor (titanium (triethanolaminate) isopropoxide) is employed, isolated titanium species are obtained. The fact that these species remain isolated even after calcination is due to the protective effect of the triethanolaminate ligand that avoids titanium polymerization. These differences in the titanium environment have a pivotal role in the performance of these systems in the epoxidation of alkenes with hydrogen peroxide.

Capel-Sanchez, M.; Blanco-Brieva, G; Campos-Martin, J; de Frutos, M; Wen, W; Rodriguez, J; Fierro, J

2009-01-01

332

Synthesis and characterization of a novel superabsorbent polymer of N, O-carboxymethyl chitosan graft copolymerized with vinyl monomers  

Microsoft Academic Search

A novel superabsorbent polymer was prepared by graft copolymerization of sodium acrylate and 1-vinyl-2-pyrrolidone onto the chain of N,O-carboxymethyl chitosan. The molecular structure of the product was confirmed by FTIR. The surface morphologies before and after the polymerization were examined by SEM. By studying the water absorption of the polymer synthesized under different conditions, the optimal conditions for synthesizing the

Yu Chen; Yun-fei Liu; Hui-min Tan; Jian-xin Jiang

2009-01-01

333

Fabrication of cationic nanomicelle from chitosan- graft-polycaprolactone as the carrier of 7-ethyl-10-hydroxy-camptothecin  

Microsoft Academic Search

In this research, amphiphilic brush-like polycations were synthesized, and used to fabricate cationic nanomicelle as the carrier of 7-ethyl-10-hydroxy-camptothecin (SN-38), in order to enhance its cellular uptake, solubility and stability in aqueous media. In particular, cationic chitosan-graft-polycaprolactone (CS-g-PCL) copolymers were synthesized with a facile one-pot manner via ring-opening polymerization of ?-CL onto the hydroxyl groups of CS by using methanesulfonic

Kongrong Duan; Xiaolan Zhang; Xiaoxing Tang; Jiahui Yu; Shiyuan Liu; Daxin Wang; Yaping Li; Jin Huang

2010-01-01

334

Antifungal activity, biofilm-controlling effect, and biocompatibility of poly(N-vinyl-2-pyrrolidinone)-grafted denture materials.  

PubMed

Colonization and biofilm-formation of Candida species on denture surfaces cause Candida-associated denture stomatitis (CADS), a common, recurring disease affecting up to 67% of denture wearers. We developed poly(N-vinyl-2-pyrrolidinone)-grafted denture materials that can be repeatedly recharged with various antifungal drugs to achieve long-term antifungal and biofilm-controlling effects. The monomer, N-vinyl-2-pyrrolidinone (NVP), was grafted onto poly(methyl methacrylate) denture resins through plasma-initiated grafting polymerization. The physical properties and biocompatibility of the resulting resins were not negatively affected by the presence of up to 7.92% of grafted poly (N-vinyl-2-pyrrolidinone) (PNVP). Miconazole and chlorhexidine digluconate (CD) were used as model antifungal drugs. PNVP grafting significantly increased the drug absorption capability of the resulting denture materials. Further, the new materials showed sustained drug release and provided antifungal effects for weeks (in the case of CD) to months (in the case of miconazole). The drug-depleted resins could be recharged with the same or a different class of antifungal drug to further extend antifungal duration. If needed, drugs on the PNVP-grafted denture materials could be "washed out" (quenched) by treating with PNVP aqueous solutions to stop drug release. These results point to great potentials of the new materials in controlling biofilm-formation in a wide range of device-related applications. PMID:23708753

Sun, Xinbo; Cao, Zhengbing; Yeh, Chih-Ko; Sun, Yuyu

2013-10-01

335

Antifungal activity, biofilm-controlling effect, and biocompatibility of poly(N-vinyl-2-pyrrolidinone)-grafted denture materials  

PubMed Central

Colonization and biofilm-formation of Candida species on denture surfaces cause Candida-associated denture stomatitis (CADS), a common, recurring disease affecting up to 67% of denture wearers. We developed poly(N-vinyl-2-pyrrolidinone)-grafted denture materials that can be repeatedly recharged with various antifungal drugs to achieve long-term antifungal and biofilm-controlling effects. The monomer, N-vinyl-2-pyrrolidinone (NVP), was grafted onto poly(methyl methacrylate) denture resins through plasma-initiated grafting polymerization. The physical properties and biocompatibility of the resulting resins were not negatively affected by the presence of up to 7.92% of grafted poly (N-vinyl-2-pyrrolidinone) (PNVP). Miconazole and chlorhexidine digluconate (CD) were used as model antifungal drugs. PNVP grafting significantly increased the drug absorption capability of the resulting denture materials. Further, the new materials showed sustained drug release and provided antifungal effects for weeks (in the case of CD) to months (in the case of miconazole). The drug-depleted resins could be recharged with the same or a different class of antifungal drug to further extend antifungal duration. If needed, drugs on the PNVP-grafted denture materials could be “washed out” (quenched) by treating with PNVP aqueous solutions to stop drug release. These results point to great potentials of the new materials in controlling biofilm-formation in a wide range of device-related applications. PMID:23708753

Sun, Xinbo; Cao, Zhengbing; Yeh, Chih-Ko; Sun, Yuyu

2013-01-01

336

Immobilization of quaternary ammonium salts on grafting particle polystyrene/SiO 2 and preliminary study of application performance  

NASA Astrophysics Data System (ADS)

Polystyrene (PSt) was grafted on the surface of silica gel particles in the manner of "grafting from" in a solution polymerization system, and grafting particles PSt/SiO 2 was obtained. The chloromethylation reaction of the grafted polystyrene was performed using a novel chloromethylation reagent, 1,4-bis(chloromethyoxy)butane which is un-carcinogenic, and grafting particles CMPS/SiO 2 was gained. Subsequently, grafted CMPS was quaternized (denoted as QPS) using tertiary amine, and finally functional composite-type particles QPS/SiO 2, on which quaternary ammonium groups were immobilized, were prepared. The catalysis activity of the particle QPS/SiO 2 as a triphase catalyst in phase-transfer catalysis systems and its antibacterial activity as a water-insoluble antibacterial material were studied preliminarily. The experimental results show that the particle QPS/SiO 2 exhibits higher catalysis activity as a triphase catalyst for the reaction between benzyl chloride in organic phase and sodium acetate in aqueous phase to form benzyl acetate, and under a mild condition of 60 °C for 7 h of reaction time a conversion of 66% for benzyl chloride can be obtained. The particle QPS/SiO 2 has high antibacterial activity as a water-insoluble antibacterial material against Escherichia coli ( E. coli).

Gao, Baojiao; Qi, Changsheng; Liu, Qing

2008-04-01

337

Surface functionalization of a polymeric lipid bilayer for coupling a model biological membrane with molecules, cells, and microstructures.  

PubMed

We describe a stable and functional model biological membrane based on a polymerized lipid bilayer with a chemically modified surface. A polymerized lipid bilayer was formed from a mixture of two diacetylene-containing phospholipids, 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DiynePC) and 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphoethanolamine (DiynePE). DiynePC formed a stable bilayer structure, whereas the ethanolamine headgroup of DiynePE enabled functional molecules to be grafted onto the membrane surface. Copolymerization of DiynePC and DiynePE resulted in a robust bilayer. Functionalization of the polymeric bilayer provided a route to a robust and biomimetic surface that can be linked with biomolecules, cells, and three-dimensional (3D) microstructures. Biotin and peptides were grafted onto the polymeric bilayer for attaching streptavidin and cultured mammalian cells by molecular recognition, respectively. Nonspecific adsorption of proteins and cells on polymeric bilayers was minimum. DiynePE was also used to attach a microstructure made of an elastomer (polydimethylsiloxan: PDMS) onto the membrane, forming a confined aqueous solution between the two surfaces. The microcompartment enabled us to assay the activity of a membrane-bound enzyme (cyochrome P450). Natural (fluid) lipid bilayers were incorporated together with membrane-bound proteins by lithographically polymerizing DiynePC/DiynePE bilayers. The hybrid membrane of functionalized polymeric bilayers and fluid bilayers offers a novel platform for a wide range of biomedical applications including biosensor, bioassay, cell culture, and cell-based assay. PMID:23347422

Morigaki, Kenichi; Mizutani, Kazuyuki; Saito, Makoto; Okazaki, Takashi; Nakajima, Yoshihiro; Tatsu, Yoshiro; Imaishi, Hiromasa

2013-02-26

338

Electrical and thermal behavior of proton irradiated polymeric blends  

Microsoft Academic Search

Polymeric blends of polyvinyl chloride (PVC) and polyethylene terephthalate (PET) have been irradiated with 3MeV proton beam at different fluences. The radiation induced changes in electrical and thermal properties were investigated by the LCR meter in the frequency range 0.1–100kHz, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy.It is found that AC conductivity increases exponentially

N. L. Singh; Nilam Shah; K. P. Singh; C. F. Desai

2005-01-01

339

Amputation of congo red dye from waste water using microwave induced grafted Luffa cylindrica cellulosic fiber.  

PubMed

The present study deals with the surface modification of Luffa cylindrica fiber through graft copolymerization of methyl acrylate/acrylamide (MA/AAm) via microwave radiation without the use of initiator. Various reaction parameters effecting grafting yield were optimized and physico-chemical properties were evaluated. The grafted Luffa cylindrica fiber showed morphological transformations, thermal stability and chemical resistance. The adsorption potential of modified fiber was investigated using adsorption isotherms for hazardous congo red dye removal from aqueous system. The maximum adsorption capacity of dye onto grafted Luffa cylindrica fiber was found to be 17.39 mg/g with best fit for Langmuir adsorption isotherm. The values of thermodynamic parameters such as enthalpy change, ?H(0) (21.27 kJ/mol), entropy change, ?S(0) (64.71 J/mol K) and free energy change, ?G(0) (-139.52 kJ/mol) were also calculated. Adsorption process was found spontaneous and endothermic in nature. PMID:25037387

Gupta, Vinod Kumar; Pathania, Deepak; Agarwal, Shilpi; Sharma, Shikha

2014-10-13

340

Stereospecific olefin polymerization catalysts  

DOEpatents

A metallocene catalyst system for the polymerization of .alpha.-olefins to yield stereospecific polymers including syndiotactic, and isotactic polymers. The catalyst system includes a metal and a ligand of the formula ##STR1## wherein: R.sup.1, R.sup.2, and R.sup.3 are independently selected from the group consisting of hydrogen, C.sub.1 to C.sub.10 alkyl, 5 to 7 membered cycloalkyl, which in turn may have from 1 to 3 C.sub.1 to C.sub.10 alkyls as a substituent, C.sub.6 to C.sub.15 aryl or arylalkyl in which two adjacent radicals may together stand for cyclic groups having 4 to 15 carbon atoms which in turn may be substituted, or Si(R.sup.8).sub.3 where R.sup.8 is selected from the group consisting of C.sub.1 to C.sub.10 alkyl, C.sub.6 to C.sub.15 aryl or C.sub.3 to C.sub.10 cycloalkyl; R.sup.4 and R.sup.6 are substituents both having van der Waals radii larger than the van der Waals radii of groups R.sup.1 and R.sup.3 ; R.sup.5 is a substituent having a van der Waals radius less than about the van der Waals radius of a methyl group; E.sup.1, E.sup.2 are independently selected from the group consisting of Si(R.sup.9).sub.2, Si(R.sup.9).sub.2 --Si(R.sup.9).sub.2, Ge(R.sup.9).sub.2, Sn(R.sup.9).sub.2, C(R.sup.9).sub.2, C(R.sup.9).sub.2 --C(R.sup.9).sub.2, where R.sup.9 is C.sub.1 to C.sub.10 alkyl, C.sub.6 to C.sub.15 aryl or C.sub.3 to C.sub.10 cycloalkyl; and the ligand may have C.sub.S or C.sub.1 -symmetry. Preferred metals are selected from the group consisting of group III, group IV, group V or lanthanide group elements. The catalysts are used to prepare stereoregular polymers including polypropylene from .alpha.-olefin monomers.

Bercaw, John E. (Pasadena, CA); Herzog, Timothy A. (Pasadena, CA)

1998-01-01

341

Stereospecific olefin polymerization catalysts  

DOEpatents

A metallocene catalyst system is described for the polymerization of {alpha}-olefins to yield stereospecific polymers including syndiotactic, and isotactic polymers. The catalyst system includes a metal and a ligand of the formula shown wherein: R{sup 1}, R{sup 2}, and R{sup 3} are independently selected from the group consisting of hydrogen, C{sub 1} to C{sub 10} alkyl, 5 to 7 membered cycloalkyl, which in turn may have from 1 to 3 C{sub 1} to C{sub 10} alkyls as a substituent, C{sub 6} to C{sub 15} aryl or arylalkyl in which two adjacent radicals may together stand for cyclic groups having 4 to 15 carbon atoms which in turn may be substituted, or Si(R{sup 8}){sub 3} where R{sup 8} is selected from the group consisting of C{sub 1} to C{sub 10} alkyl, C{sub 6} to C{sub 15} aryl or C{sub 3} to C{sub 10} cycloalkyl; R{sup 4} and R{sup 6} are substituents both having van der Waals radii larger than the van der Waals radii of groups R{sup 1} and R{sup 3}; R{sup 5} is a substituent having a van der Waals radius less than about the van der Waals radius of a methyl group; E{sup 1}, E{sup 2} are independently selected from the group consisting of Si(R{sup 9}){sub 2}, Si(R{sup 9}){sub 2}--Si(R{sup 9}){sub 2}, Ge(R{sup 9}){sub 2}, Sn(R{sup 9}){sub 2}, C(R{sup 9}){sub 2}, C(R{sup 9}){sub 2}--C(R{sup 9}){sub 2}, where R{sup 9} is C{sub 1} to C{sub 10} alkyl, C{sub 6} to C{sub 15} aryl or C{sub 3} to C{sub 10} cycloalkyl; and the ligand may have C{sub S} or C{sub 1}-symmetry. Preferred metals are selected from the group consisting of group III, group IV, group V or lanthanide group elements. The catalysts are used to prepare stereoregular polymers including polypropylene from {alpha}-olefin monomers.

Bercaw, J.E.; Herzog, T.A.

1998-01-13

342

Space environmental effects on polymeric materials  

NASA Technical Reports Server (NTRS)

Polymeric materials that may be exposed on spacecraft to the hostile environment beyond Earth's atmosphere were subjected to atomic oxygen, electron bombardment, and ultraviolet radiation in terrestrial experiments. Evidence is presented for the utility of an inexpensive asher for determining the relative susceptibility of organic polymers to atomic oxygen. Kapton, Ultem, P1700 polysulfone, and m-CBB/BIS-A (a specially formulated polymer prepared at NASA Langley) all eroded at high rates, just as was observed in shuttle experiments. Films of Ultem, P1700 polysulfone, and m-CBB/BIS-A were irradiated with 85 keV electrons. The UV/VIS absorbance of Ultem was found to decay with time after irradiation, indicating free radical decay. The tensile properties of Ultem began to change only after it had been exposed to 100 Mrads. The effects of dose rate, temperature, and simultaneous vs. sequential electron and UV irradiation were also studied.

Kiefer, Richard L.; Orwoll, Robert A.

1987-01-01

343

Model For Bending Actuators That Use Electrostrictive Graft Elastomers  

NASA Technical Reports Server (NTRS)

Recently, it was reported that an electrostrictive graft elastomer exhibits large electric field-induced strain (4%). Combined with its high mechanical modulus, the elastomer can offer very promising electromechanical properties, in terms of output mechanical energy density, for an electroactive polymeric material. Therefore, it has been considered as one of the candidates that can be used in high performance, low mass actuation devices in many aerospace applications. Various bilayer- based bending actuators have been designed and fabricated. An analytic model based on beam theory in the strength of materials has been derived for the transverse deflection, or curvature, and the longitudinal strain of the bi-layer beam. The curvature and strain are functions of the applied voltage and the thickness, width, and Young s modulus of the active and passive layers. The model can be used to optimize the performance of electrostrictive graft elastomer-based actuators to meet the requirements of various applications. In this presentation, optimization and sensitivity studies are applied to the bending performance of such actuators.

Costen, Robert C.; Su, Ji; Harrison, Joycelyn S.

2001-01-01

344

Design and synthesis of pH-responsive polymeric carriers that target uptake and enhance the intracellular delivery of oligonucleotides  

Microsoft Academic Search

The delivery of biomolecular therapeutics that function intracellularly remains a significant challenge in the field of biotechnology. In this report, a new family of polymeric drug carriers that combine cell targeting, a pH-responsive membrane-disruptive component, and serum-stabilizing polyethylene glycol (PEG) grafts, is shown to direct the uptake and endosomal release of oligonucleotides in a primary hepatocyte cell line. These polymers

Niren Murthy; Jean Campbell; Nelson Fausto; Allan S. Hoffman; Patrick S. Stayton

2003-01-01

345

Severe impairment of graft flow without electrocardiographic changes during coronary artery bypass grafting.  

PubMed

Early graft occlusion after coronary artery bypass grafting may have deleterious consequences. We routinely use transit-time flowmetry after termination of cardiopulmonary bypass, and we report five cases of early graft failure detected by the flowmeter. Electrocardiographic (ECG) changes were seen in only one of these five cases, and none of the patients had low cardiac output or other signs of graft failure at the end of the operation. The cause of graft failure was tagging in one case, rotation of internal mammary artery grafts in two and kinking of vein grafts in two cases. All errors were corrected, and control flowmetry showed normal flow rates after correction. Flowmetry takes less than 10 min, even with multiple bypass grafts. Based on our results, we advocate routine quality control with flowmetry after termination of cardiopulmonary bypass, since ECG changes are insufficient as checks of flow in bypass grafts. PMID:10399803

Jakobsen, H L; Kjaergard, H K

1999-01-01

346

On-demand photoinitiated polymerization  

DOEpatents

Compositions and methods for adjustable lenses are provided. In some embodiments, the lenses contain a lens matrix material, a masking compound, and a prepolymer. The lens matrix material provides structure to the lens. The masking compound is capable of blocking polymerization or crosslinking of the prepolymer, until photoisomerization of the compound is triggered, and the compound is converted from a first isomer to a second isomer having a different absorption profile. The prepolymer is a composition that can undergo a polymerization or crosslinking reaction upon photoinitiation to alter one or more of the properties of the lenses.

Boydston, Andrew J; Grubbs, Robert H; Daeffler, Chris; Momcilovic, Nebojsa

2013-12-10

347

Tunnel magnetoresistance of polymeric chains  

E-print Network

Coherent spin-dependent electronic transport is investigated in a molecular junction made of polymeric chain attached to ferromagnetic electrodes (Ni and Co, respectively). Molecular system is described by a simple Huckel model, while the coupling to the electrodes is treated through the use of a broad-band theory. The current flowing through the device is calculated within non-equilibrium Green's function approach. It is shown that tunnel magnetoresistance of molecular junction can be quite large (over 100 %)and strongly depends on: (i) the lenght of the polymeric chain and (ii) the strength of the molecule-to-electrodes coupling.

Kamil Walczak

2004-10-25

348

Colloidal Dispersions in Polymeric Media: Interparticle Forces, Microstructure and Rheology  

NASA Astrophysics Data System (ADS)

To enhance properties of the ultimate materials, melt processed polymers are commonly filled with colloidal particles, such as inorganic oxides. Dispersing such particles in a melt is generally difficult due to the strong van der Waals attractions. These attractive forces can be modulated through surface modifications such as polymer adsorption and grafting. Indeed, the relative viscosity of 430 nm Al2O3particles stabilized by end-tethered poly(dimethylsiloxane) (PDMS) in PDMS melts decreases with increasing graft density and molecular weight as expected, but also with increasing molecular weight of the melt, contrary to well established theories. The relative steady shear viscosity exhibits neither a low shear limit nor a yield stress, but follows a power law characterized by relative high shear viscosity (eta infinity/mu) and a structural relaxation time (tau). The measured structural time can be correlated reasonably well with a characteristic relaxation time, tauo, estimated by equating the viscous resistance with the maximum attractive force. We further explored the significance of this power law with TiO2 nanoparticles in PDMS melts with a reduction in size and an increase in Hamaker constant. Bare, octadecyl-coated, and 9k-PDMS grafted TiO2 particles dispersed in neat and binary PDMS melts revealed behavior similar to that of the large alumina particles, as the increased strength of van der Waals forces offset the reduction in size. To complete the study ZrO2 nanoparticles were dispersed in solution of associative polymers and characterized by small amplitude oscillatory shear. The data exhibits two relaxation modes: Maxwellian behavior at high frequency imparted by the associating polymers and a power law spectrum at low frequency from the particles. The timescales and volume fraction dependence reflect the attractions between particles with adsorbed polymer layers dispersed in a percolated network of associative polymers. Together these studies demonstrate the range and origin of the rheology possible with particles dispersed in polymeric media.

Ndong, Rose Seynabou

349

Segmentation strategies for polymerized volume data sets  

E-print Network

A new technique, called the polymerization algorithm, is described for the hierarchical segmentation of polymerized volume data sets (PVDS) using the Lblock data structure. The Lblock data structure is defined as a 3dimensional isorectangular block...

Doddapaneni, Venkata Purna

2006-04-12

350

Poly(ether-ether-ketone) orthopedic bearing surface modified by self-initiated surface grafting of poly(2-methacryloyloxyethyl phosphorylcholine).  

PubMed

We investigated the production of free radicals on a poly(ether-ether-ketone) (PEEK) substrate under ultraviolet (UV) irradiation. The amount of the ketyl radicals produced from the benzophenone (BP) units in the PEEK molecular structure initially increased rapidly and then became almost constant. Our observations revealed that the BP units in PEEK acted as photoinitiators, and that it was possible to use them to control the graft polymerization of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC). This "self-initiated surface graft polymerization" method is very convenient in the absence of external photoinitiator. We also investigated the effects of the monomer concentration and UV irradiation time on the extent of the grafted PMPC layer. Furthermore, as an application to improving the durability of artificial hips, we demonstrated the nanometer-scale photoinduced grafting of PMPC onto PEEK and carbon fiber-reinforced PEEK (CFR-PEEK) orthopedic bearing surfaces and interfaces. A variety of test revealed significant improvements in the water wettability, frictional properties, and wear resistance of the surfaces and interfaces. PMID:23891520

Kyomoto, Masayuki; Moro, Toru; Yamane, Shihori; Hashimoto, Masami; Takatori, Yoshio; Ishihara, Kazuhiko

2013-10-01

351

Temperature-dependent conformational changes of PNIPAM grafted chains in water : effects of molecular weight and grafting density.  

SciTech Connect

Poly(N-isopropyl acrylamide) (PNIPAM) is perhaps the most well known member of the class of responsive polymers. Free PNIPAM chains have a lower critical solution temperature in water at {approx}31 C. This very sharp transition ({approx}5 C) is attributed to alterations in the hydrogen bonding interactions of the amide group. Grafted chains of PNIPAM have shown promise for creating responsive surfaces. Examples include controlling the adsorption of proteins or bacteria, regulating the flow of liquids in narrow filaments or mesoporous materials, control of enzymatic activity, and releasing the contents of liposomes. Conformational changes of the polymer are likely to play a role in some of these applications, in addition to changes in local interactions. In this work we investigated the T-dependent conformational changes of grafted PNIPAM chains in D2O using neutron reflection and AFM. The molecular weight (M) and surface density of the PNIPAM brushes were controlled using atom-transfer radical polymerization. We discovered a strong effect of surface density. At lower surface densities, in the range typically achieved with grafting-to methods, we observed very little conformational change. At higher surface densities, significant changes with T were observed. The results will be compared with numerical SCF calculations employing an effective (conc.-dependent) Flory-Huggins chi parameter extracted from the solution phase diagram. For the case of high M and high surface density, a non-monotonic change in profile shape with T was observed. This will be discussed in the context of vertical phase separation predicted for brushes of water-soluble polymers within two-state models.

Satija, Sushil K. (National Institute of Standards and Technology, Gaithersburg, MD); Mendez, Sergio (University of New Mexico, Albuquerque, NM); Kent, Michael Stuart; Yim, Hyun; Lopez, Gabriel P. (University of New Mexico, Albuquerque, NM)

2005-03-01

352

Nonlinear optical and conductive polymeric material  

DOEpatents

A polymeric material is described which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl[sub 5] or W(CO)[sub 6].

Barton, T.J.; Ijadi-Maghsooodi, S; Yi Pang.

1993-10-19

353

Nonlinear optical and conductive polymeric material  

DOEpatents

A polymeric material which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl.sub.5 or W(CO).sub.6 /hv.

Barton, Thomas J. (Ames, IA); Ijadi-Maghsoodi, Sina (Ames, IA); Pang, Yi (Ames, IA)

1992-05-19

354

Nonlinear optical and conductive polymeric material  

DOEpatents

A polymeric material which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl[sub 5] or W(CO)[sub 6]/hv.

Barton, T.J.; Ijadi-Maghsoodi, S.; Pang, Y.

1992-05-19

355

Nonlinear optical and conductive polymeric material  

DOEpatents

A polymeric material which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl.sub.5 or W(CO).sub.6 /hv.

Barton, Thomas J. (Ames, IA); Ijadi-Maghsoodi, Sina (Ames, IA); Pang, Yi (Ames, IA)

1993-10-19

356

Polymerization of safflower and rapeseed oils  

Microsoft Academic Search

Rates of polymerization of oils from 2 safflower and 2 rapeseed varieties were measured in the air and under vacuum. Thermal\\u000a polymerization rates showed a stronger dependence on the degree of unsaturation than on oxidative polymerization. Molecular\\u000a weight distributions of polymerized oils were determined by size exclusion chromatography, and the relationship between viscosity\\u000a and weight-average molecular weight was determined.

Roger A. Korus; Traci L. Mousetis

1984-01-01

357

Reverse atom transfer radical polymerization (RATRP) for anti-clotting PU-LaCl3-g-P(MPC) films  

NASA Astrophysics Data System (ADS)

Low grafting density is a disadvantage both in reverse atom transfer radical polymerization (RATRP) and ATRP. In this work, the surfaces of polyurethane (PU) were treated by LaCl3·6H2O to obtain modified surfaces with hydrated layers. The reaction of surface-initiated RATRP was carried out easily, which may be attributed to the enriched hydroxyl groups on the hydrated layers. An innovation found in this work is that some free lanthanum ions (La3+) reacted with the silane coupling agent (CPTM) and the product served as mixed ligand complex. The mixed ligand complex instead of conventional 2,2?-bipyridine was adopted to serve as a ligand in the process of RATRP. As a result, PU surfaces grafted with well-defined polymer brushes (MPC) were obtained. PU substrates before and after modification were characterized by FTIR, XPS, AFM, SEM, SCA, respectively. The results showed that zwitterionic brushes were successfully fabricated on the PU surfaces (P(MPC)), and the content of the grafted layer increased gradually with polymerization time with the grafting density as high as 97.9%. The blood compatibility of the PU substrates was evaluated by plasma recalcification profiles test and platelet adhesion tests in vitro. It was found that all PU functionalized with zwitterionic brush showed improved resistance to nonspecific protein adsorption and platelet adhesion.

Lu, Chunyan; Zhou, Ninglin; Xiao, Yinghong; Tang, Yida; Jin, Suxing; Wu, Yue; Shen, Jian

2013-01-01

358

Competition between side chain length and side chain distribution: Searching for optimal polymeric architectures for application in fuel cell membranes  

NASA Astrophysics Data System (ADS)

Microphase separation within 10 polymeric membranes of similar ion exchange capacity is studied by dissipative particle dynamics (DPD). The polymers consist of hydrophobic A and hydrophilic C fragments. For 8 grafted architectures, the side chains ([C], [AC], [AAC], or [AAAC]) are distributed uniformly or pairwise along the hydrophobic backbone. For the other 2 (block type) architectures the C fragments are uniformly and pairwise distributed within the backbone, respectively. For the water containing pore networks the following trends are found: For the uniform architectures, the pore size is lowest for the block- and increases further for the grafted architectures with increase of side chain length, while for the pairwise architectures the reverse trend is observed. Water diffusion through the hydrophilic pore networks is deduced from Monte Carlo tracer diffusion calculations (through 800 snapshots). Among the uniform architectures diffusion is highest for the grafted architecture with long [AAAC] side chains. Interestingly, for the pairwise architectures diffusion is highest for the grafted polymers with the short ([C]) side chains. Side chain length and side chain distribution are thus predicted to be interesting design parameters in order to optimize proton and or solvent transport within flexible amphiphilic polymeric membranes.

Dorenbos, G.

2015-02-01

359

Molecularly Oriented Polymeric Thin Films for Space Applications  

NASA Technical Reports Server (NTRS)

The increased commitment from NASA and private industry to the exploration of outer space and the use of orbital instrumentation to monitor the earth has focused attention on organic polymeric materials for a variety of applications in space. Some polymeric materials have exhibited short-term (3-5 yr) space environmental durability; however, future spacecraft are being designed with lifetimes projected to be 10-30 years. This gives rise to concern that material property change brought about during operation may result in unpredicted spacecraft performance. Because of their inherent toughness and flexibility, low density, thermal stability, radiation resistance and mechanical strength, aromatic polyimides have excellent potential use as advanced materials on large space structures. Also, there exists a need for high temperature (200-300 C) stable, flexible polymeric films that have high optical transparency in the 300-600nm range of the electromagnetic spectrum. Polymers suitable for these space applications were fabricated and characterized. Additionally, these polymers were molecularly oriented to further enhance their dimensional stability, stiffness, elongation and strength. Both unoriented and oriented polymeric thin films were also cryogenically treated to temperatures below -184 C to show their stability in cold environments and determine any changes in material properties.

Fay, Catharine C.; Stoakley, Diane M.; St.Clair, Anne K.

1997-01-01

360

X-ray initiated polymerization of wood impregnants  

NASA Astrophysics Data System (ADS)

X-rays, derived from a high energy, high-current electron beam (EB), initiated in-situ polymerization of a unique class of monomers that were found to penetrate the cell walls of wood. X-rays initiated an auto-catalytic acrylic polymerization and penetrated through thick pieces of wood. The final cured product having the polymerizate, a polymer, both in the wood cell lumens and in the cell walls is called wood impregnated with a wood-polymer penetrant (WPP). The controlled lower dose rate of X-rays overcame disproportionation encountered when using higher dose-rate electron beam initiation. With X-rays, the in-situ polymerization took place in one exposure of modest dose. With EB, multiple passes were needed to avoid excessive heat build-up and monomer volatilization. Having entered the cell walls of the wood and then being polymerized within the cell walls, these radiation-cured unique monomers imparted outstanding dimensional stability upon exposure of the impregnated wood to humidity cycling. The preferred monomer system was also chemically modified prior to impregnation with agents that would remain in the wood and prevent the growth of fungi and other microbials. This technique differs from historic uses of monomers that merely filled the lumens of the wood (historic wood-polymer composites), which are only suitable for indoor use. The WPP impregnated wood that was either X-ray cured or EB cured demonstrated enhanced structural properties, dimensional stability, and decay resistance.

Cleland, Marshall R.; Galloway, Richard A.; Berejka, Anthony J.; Montoney, Daniel; Driscoll, Mark; Smith, Leonard; Scott Larsen, L.

2009-07-01

361

Attempting a classification for electrical polymeric actuators  

Microsoft Academic Search

Polymeric actuators, electroactive polymer actuators, electromechanical polymeric actuators, artificial muscles, and other, are usual expressions to name actuators developed during the last 15-20 years based on interactions between the electric energy and polymer films. The polymeric actuators can be divided into two main fields: electromechanical actuators working by electrostatic interactions between the polymer and the applied electric fields, and electrochemomechanical

T. F. Otero; J. López Cascales; A. J. Fernández-Romero

2007-01-01

362

Outdoor HV composite polymeric insulators  

Microsoft Academic Search

HV composite polymeric insulators are being accepted increasingly for use in outdoor installations by the traditionally cautious electric power utilities worldwide. They currently represent ~60 to 70% of newly installed HV insulators in North America. The tremendous growth in the applications of non-ceramic composite insulators is due to their advantages over the traditional ceramic and glass insulators. These include light

R. Hackam

1999-01-01

363

The Viscosity of Polymeric Fluids.  

ERIC Educational Resources Information Center

To illustrate the behavior of polymeric fluids and in what respects they differ from Newtonian liquids, an experiment was developed to account for the shear-rate dependence of non-Newtonian fluids. Background information, procedures, and results are provided for the experiment. Useful in transport processes, fluid mechanics, or physical chemistry…

Perrin, J. E.; Martin, G. C.

1983-01-01

364

POLYMERIC INTERFACES FOR STACK MONITORING  

EPA Science Inventory

Research has been performed on the use of polymeric interfaces for in situ continuous stack monitoring of gaseous pollutants. Permeabilities of candidate interface materials to SO2 were measured at temperatures from ambient to 200C, and the results were used to design interfaces ...

365

Low vibration polymeric composite engine  

NASA Astrophysics Data System (ADS)

An internal combustion engine is constructed with metallic parts in its regions which are subjected to high stress (temperature, pressure) during combustion and polymeric materials in its regions which are subjected to relatively lower stresses. The integrated construction helps realize increased power densities and reductions on engine noise without compromising engine performance. V-configuration Diesel engines particularly benefit from this construction.

Guimond, David P.; Muench, Rolf K.

1994-12-01

366

Sleeving nanocelluloses by admicellar polymerization.  

PubMed

This investigation reports the first application of admicellar polymerization to cellulose nanofibers in the form of bacterial cellulose, microfibrillated cellulose, and cellulose nanowhiskers using styrene and ethyl acrylate. The success of this physical sleeving was assessed by SEM, FTIR, and contact angle measurements, providing an original and simple approach to the modification of cellulose nanofibers in their pristine aqueous environment. PMID:23921337

Trovatti, Eliane; Ferreira, Adriane de Medeiros; Carvalho, Antonio José Felix; Ribeiro, Sidney José Lima; Gandini, Alessandro

2013-10-15

367

Controlled grafting of well-defined epoxide polymers on hydrogen-terminated silicon substrates by surface-initiated ATRP at ambient temperature.  

PubMed

Controlled grafting of well-defined epoxide polymer brushes on the hydrogen-terminated Si(100) substrates (Si-H substrates) was carried out via the surface-initiated atom-transfer radical polymerization (ATRP) at room temperature. Thus, glycidyl methacrylate (GMA) polymer brushes were prepared by ATRP from the alpha-bromoester functionalized Si-H surface. Kinetic studies revealed a linear increase in GMA polymer (PGMA) film thickness with reaction time, indicating that chain growth from the surface was a controlled "living" process. The graft polymerization proceeded more rapidly in the dimethylformamide/water (DMF/H(2)O) mixed solvent medium than in DMF, leading to much thicker PGMA growth on the silicon surface in the former medium. The chemical composition of the GMA graft-polymerized silicon (Si-g-PGMA) surfaces were characterized by X-ray photoelectron spectroscopy (XPS). The fact that the epoxide functional groups of the grafted PGMA were preserved quantitatively was revealed in the reaction with ethylenediamine. The "living" character of the PGMA chain end was further ascertained by the subsequent growth of a poly(pentafluorostyrene) (PFS) block from the Si-g-PGMA surface, using the PGMA brushes as the macroinitiators. PMID:15350105

Yu, W H; Kang, E T; Neoh, K G

2004-09-14

368

Skeletal Muscle Regeneration on Protein-Grafted and Microchannel-Patterned Scaffold for Hypopharyngeal Tissue Engineering  

PubMed Central

In the field of tissue engineering, polymeric materials with high biocompatibility like polylactic acid and polyglycolic acid have been widely used for fabricating living constructs. For hypopharynx tissue engineering, skeletal muscle is one important functional part of the whole organ, which assembles the unidirectionally aligned myotubes. In this study, a polyurethane (PU) scaffold with microchannel patterns was used to provide aligning guidance for the seeded human myoblasts. Due to the low hydrophilicity of PU, the scaffold was grafted with silk fibroin (PU-SF) or gelatin (PU-Gel) to improve its cell adhesion properties. Scaffolds were observed to degrade slowly over time, and their mechanical properties and hydrophilicities were improved through the surface grafting. Also, the myoblasts seeded on PU-SF had the higher proliferative rate and better differentiation compared with those on the control or PU-Gel. Our results demonstrate that polyurethane scaffolds seeded with myoblasts hold promise to guide hypopharynx muscle regeneration. PMID:24175281

Shen, Zhisen; Guo, Shanshan; Ye, Dong; Chen, Jingjing; Kang, Cheng; Qiu, Shejie; Lu, Dakai; Li, Qun; Xu, Kunjie; Lv, Jingjing

2013-01-01

369

High Surface Area Poly(3-hexylthiophenes) Thin Films from Cleavable Graft Copolymers  

SciTech Connect

A strategy for the fabrication of high surface area poly(3-hexylthiophene) thin films by removal of nanoscale domains formed from graft copolymers is presented. This approach relies on the synthesis and characterization of cleavable graft copolymers based on regioregular poly(3-hexylthiophene) (rr-P3HT) main chain and sacrificial poly(styrene) side chains. An alkoxyamine initiator based on 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) was incorporated at the 3-position of the functionalized thienyl repeat unit, 2, via a cleavable trityl ether linker. Grignard metathesis (GRIM) copolymerization of 2 and 2,5-dibromo-3-hexylthiophene afforded regioregular P3HT with randomly incorporated alkoxyamine groups. Polymerization of styrene from the P3HT backbone for different time periods afforded graft copolymers with controllable sacrificial chain lengths. These materials were characterized using an array of techniques such as {sup 1}H and {sup 13}C NMR spectroscopy and size exclusion chromatography (SEC). An approach to obtain nanoporous P3HT thin films by cleavage of the trityl ether linker followed by complete removal of poly(styrene) is reported with the as-cast graft copolymer thin films displaying an irregular microphase-separated structure with an average domain size {approx}30 nm as determined by grazing incidence small-angle X-ray scattering (GISAXS) measurements. Significantly, this length scale was conserved after removal of the sacrificial component which allows this strategy to have potential application in diverse fields such as organic photovoltaics.

Sivanandan, Kulandaivelu; Chatterjee, Tirtha; Treat, Neil; Kramer, Edward J.; Hawker, Craig J. (UCSB)

2010-03-30

370

Synthesis and solution behavior of poly(?-caprolactone) grafted hydroxyethyl cellulose copolymers.  

PubMed

Trimethylsilylated hydroxyethyl cellulose (TMSHEC) was synthesized by using hexamethyldisilazane (HMDS) as silylated agent. With the partial protection of hydroxyl groups of HEC by silylation, the novel poly(?-polycaprolactone) (PCL) grafted HEC (HEC-g-PCL) copolymers were successfully prepared by homogenous ring-opening graft polymerization and deprotection procedure. The structure of HEC-g-PCL copolymers was characterized by FTIR and 1H NMR. Fluorescence spectrum of HEC-g-PCL copolymer dilute solution indicated that copolymers could associate and form hydrophobic microdomains in aqueous solution. With the increasing of grafted PCL content, the critical association concentration (cac) of HEC-g-PCL copolymers decreased. The surface tension of HEC-g-PCL copolymers decreased dramatically with the increasing of the concentration and then approached to a plateau value when concentration was above the cac of HEC-g-PCL copolymers. The hydrodynamic radius of the aggregate of copolymer in dilute solution was found to increase with the increasing of the grafted PCL content. When the concentration of copolymer was above the cac, the zero-shear viscosity of the copolymer increased sharply and became much higher than that of HEC at the same concentration. PMID:21093476

Jiang, Chao; Wang, Xinling; Sun, Peidong; Yang, Cheng

2011-01-01

371

Extraction of palm tree cellulose and its functionalization via graft copolymerization.  

PubMed

The work in this paper was planned with the aim of extracting the cellulosic component of palm tree waste and functionalizing this cellulose through graft copolymerization with acrylic acid. The cellulose extraction included hot alkali treatment with aqueous sodium hydroxide to remove the non-cellulosic binding materials. The alkali treatment was followed by an oxidative bleaching using peracid/hydrogen peroxide mixture with the aim of removing the rest of non-cellulosic materials to improve the fiber hydrophilicity and accessibility towards further grafting reaction. Optimum conditions for cellulose extraction are boiling in 5% (W/V) NaOH in a material to liquor ratio of 1:20 for 1 h then bleaching with 60 ml/l bleaching mixture at initial pH value of 6.5 for 30 min. The pH of the bleaching medium is turned to the alkaline range 11 and bleaching continues for extra 30 min. Graft copolymerization reaction was initiated by potassium bromate/thiourea dioxide redox system. Optimum conditions for grafting are 30 mmol of potassium bromate, 30 mmol of thiourea dioxide and 150 g of acrylic acid (each per 100 g of cellulose). The polymerization reaction was carried out for 120 min at 50°C using a material to liquor ratio of 1:20. PMID:25020080

Al-Hoqbani, Abdulmajeed A; Abdel-Halim, E S; Al-Deyab, Salem S

2014-09-01

372

Tensile Properties of Polyimide Composites Incorporating Carbon Nanotubes-Grafted and Polyimide-Coated Carbon Fibers  

NASA Astrophysics Data System (ADS)

The tensile properties and fracture behavior of polyimide composite bundles incorporating carbon nanotubes-grafted (CNT-grafted) and polyimide-coated (PI-coated) high-tensile-strength polyacrylonitrile (PAN)-based (T1000GB), and high-modulus pitch-based (K13D) carbon fibers were investigated. The CNT were grown on the surface of the carbon fibers by chemical vapor deposition. The pyromellitic dianhydride/4,4'-oxydianiline PI nanolayer coating was deposited on the surface of the carbon fiber by high-temperature vapor deposition polymerization. The results clearly demonstrate that CNT grafting and PI coating were effective for improving the Weibull modulus of T1000GB PAN-based and K13D pitch-based carbon fiber bundle composites. In addition, the average tensile strength of the PI-coated T1000GB carbon fiber bundle composites was also higher than that of the as-received carbon fiber bundle composites, while the average tensile strength of the CNT-grafted T1000GB, K13D, and the PI-coated K13D carbon fiber bundle composites was similar to that of the as-received carbon fiber bundle composites.

Naito, Kimiyoshi

2014-09-01

373

Surface-initiated polymerization from barium titanate nanoparticles for hybrid dielectric capacitors.  

PubMed

A phosphonic acid is used as a surface initiator for the growth of polystyrene and polymethylmethacrylate (PMMA) from barium titanate (BTO) nanoparticles through atom transfer radical polymerization with activators regenerated by electron transfer. This results in the barium titanate cores embedded in the grafted polymer. The one-component system, PMMA-grafted-BTO, achieves a maximum extractable energy density of 2 J/cm(3) at a field strength of ?220 V/?m, which exhibits a 2-fold increase compared to that of the composite without covalent attachment or the neat polymer. Such materials have potential applications in hybrid capacitors due to the high permittivity of the nanoparticles and the high breakdown strength, mechanical flexibility, and ease of processability due to the organic polymer. The synthesis, processing, characterization, and testing of the materials in capacitors are discussed. PMID:24490753

Paniagua, Sergio A; Kim, Yunsang; Henry, Katherine; Kumar, Ritesh; Perry, Joseph W; Marder, Seth R

2014-03-12

374

Surface modification of silicate glass using 3-(mercaptopropyl)trimethoxysilane for thiol-ene polymerization.  

PubMed

A thiol-ene polymerization was accomplished on silicate glass slides to graft a series of homopolymers and copolymers using 3-(mercaptopropyl)trimethoxysilane (MTS) as both a silane coupling agent and initiator. MTS was initially covalently bonded to an acid cleaned glass surface via a classical sol-gel reaction. Poly(acrylic acid) (PAA), poly(acrylamide) (PAAm), poly(methyl acrylate) (PMA), poly(acrylamido-2-methyl-propanesulfonic acid) (PAMPS), and the copolymer poly(AA-co-AAm-co-MA-co-AMPS) were grafted from the thiol group of MTS. The surface chemistry of the MTS modified slides and polymer grafts was characterized with attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Surface texture was evaluated with tapping mode atomic force microscopy (TM-AFM). The Owens-Wendt-Kaelble (OWK) and Lifshitz-van der Waals acid-base (LW-AB) methods were used to evaluate surface energies by sessile drop contact angle method. The synthetic approach demonstrated a facile, rapid method for grafting to glass surfaces. PMID:21870797

Chen, Jiun-Jeng; Struk, Kimberly N; Brennan, Anthony B

2011-11-15

375

Peyronie's surgery: graft choices and outcomes.  

PubMed

Peyronie's disease (PD), a localized fibrosis of the tunica albuginea surrounding the penile corpora, results in penile curvature and sexual dysfunction. Men with significant penile curvature and satisfactory erectile function are often treated with plaque incision or excision and grafting. The advantages and disadvantages of various grafting materials have long been debated. Graft materials can be divided into three categories: autologous tissue harvested from the patient's body, allograft or xenograft from another person or species, and synthetic grafts. Despite groundbreaking advances in physiology, synthetic materials, and tissue engineering, the ideal graft material has yet to be established. This review presents and discusses the variety of graft materials available for the surgical correction of PD. For this purpose, a MEDLINE search was conducted on PD until May 2009. PMID:19863858

Lentz, Aaron C; Carson, Culley C

2009-11-01

376

Wound Tissue Can Utilize a Polymeric Template to Synthesize a Functional Extension of Skin  

NASA Astrophysics Data System (ADS)

Prompt and long-term closure of full-thickness skin wounds in guinea pigs and humans is achieved by applying a bilayer polymeric membrane. The membrane comprises a top layer of a silicone elastomer and a bottom layer of a porous cross-linked network of collagen and glycosaminoglycan. The bottom layer can be seeded with a small number of autologous basal cells before grafting. No immunosuppression is used and infection, exudation, and rejection are absent. Host tissue utilizes the sterile membrane as a culture medium to synthesize neoepidermal and neodermal tissue. A functional extension of skin over the entire wound area is formed in about 4 weeks.

Yannas, I. V.; Burke, J. F.; Orgill, D. P.; Skrabut, E. M.

1982-01-01

377

Assessment of palmitoyl and sulphate conjugated glycol chitosan for development of polymeric micelles  

PubMed Central

Introduction:Amphiphilic copolymers are capable of forming core shell-like structures at the critical micellar concentration (CMC); hence, they can serve as drug carriers. Thus, in the present work, polymeric micelles based on novel chitosan derivative were synthesized. Methods:Block copolymer of palmitoyl glycol chitosan sulfate (PGCS) was prepared by grafting palmitoyl and sulfate groups serving as hydrophobic and hydrophilic fractions, respectively. Then, fourier transform infrared spectra (FTIR) and spectral changes in iodine/iodide mixture were carried out. Results:FTIR studies confirmed the formation of palmitoyl glycol chitosan sulfate (PGCS) and spectral changes in iodine/iodide mixture indicated CMC which lies in the range of 0.003-0.2 mg/ml. Conclusion: Therefore, our study indicated that polymeric micelles based on palmitoyl glycol chitosan sulphate could be used as a prospective carrier for water insoluble drugs. PMID:23878793

Ullah Khan, Ikram; Ayub, Gohar; Ranjha, Nazar M.

2013-01-01

378

On the Modification of Chitosan Through Grafting  

Microsoft Academic Search

The feasibility of grafting poly(methyl acrylate) and poly[1-(methoxycarbonyl) ethylene] onto chitosan, poly-?(1?-4)-2-amino-2-deoxy-d-glucose, was investigated. The grafting reaction was carried out in aqueous solution by using ferrous ammonium sulfate (FAS) in combination with H2O2 as redox initiator. The effects of such reaction variables as chitosan, monomer and initiator concentrations, reaction time, and reaction temperature were determined. Through this study the grafting

M. Yazdani-Pedram; A. Lagos; J. Retuert; R. Guerrero; P. Riquelme

1995-01-01

379

Silk grafting with chitosan and crosslinking agents  

Microsoft Academic Search

Chitosan grafting onto silk was tested with three crosslinking agents: trifunctional epoxy resin Araldite DY-T, PEG400 dimethacrylate,\\u000a and glutaraldehyde in acetic as well as in tartaric acid solutions. Operating conditions were studied to obtain a significant\\u000a silk weighting with satisfactory graft yields. With the epoxy crosslinker the weight gain was in the range from 1.8 to 8.8\\u000a % with graft

Franco Ferrero; Monica Periolatto; Sara Burelli; Riccardo A. Carletto

2010-01-01

380

Tensioning of the anterior cruciate ligament graft.  

PubMed

A great deal in variability exists in the protocols for graft tensioning. Biologic studies have not been conclusive about the optimum tension for revascularization while minimizing stress relaxation. Clinically, the risk of undertensioning the graft, and thereby not correcting the laxity, must be balanced with the risk of overconstraining the knee, which may lead to pathologic stresses on the joint cartilage, graft failure, or infrapatellar contracture syndrome . Amis and Jakob reported at the European Society of Sports Traumatology Knee Surgery and Arthroscopy scientific workshop in 1998 that most surgeons chose to impose a graft tension of 20 N to 80 N at an average of 11 degrees flexion. Preloading in full or nearly full extension limits the risk of pathologic stresses that can occur at full extension when the graft is tensioned at 30 degrees, but increases the risk of laxity at that angle. For our flexion parameters, we recommend tensioning the graft at 20 degrees to 30 degrees unless the graft tightens or shortens 5 mm or more with knee extension. If shortening occurs, tensioning should be performed in extension. The magnitude of graft tensioning should be tissue specific. For bone-patellar tendon-bone autograft or allograft, 5 pounds of tension should be applied. For hamstring graft, we apply 15 pounds of tension with each bundle tensioned individually. PMID:12528911

Heis, Forest T; Paulos, Leon E

2002-10-01

381

What to Expect during Coronary Artery Bypass Grafting  

MedlinePLUS

... NHLBI on Twitter. What To Expect During Coronary Artery Bypass Grafting Coronary artery bypass grafting (CABG) requires ... surgery to newer, less-invasive methods. Traditional Coronary Artery Bypass Grafting This type of surgery usually lasts ...

382

What Are the Risks of Coronary Artery Bypass Grafting?  

MedlinePLUS

... on Twitter. What Are the Risks of Coronary Artery Bypass Grafting? As with any type of surgery, ... Artery Bypass Grafting, visit www.clinicaltrials.gov . Coronary Artery Bypass Grafting in the News November 18, 2014 ...

383

Metal containing polymeric functional microspheres  

NASA Technical Reports Server (NTRS)

Polymeric functional microspheres containing metal or metal compounds are formed by addition polymerization of a covalently bondable olefinic monomer such as hydroxyethylmethacrylate in the presence of finely divided metal or metal oxide particles, such as iron, gold, platinum or magnetite, which are embedded in the resulting microspheres. The microspheres can be covalently bonded to chemotherapeutic agents, antibodies, or other proteins providing a means for labeling or separating labeled cells. Labeled cells or microspheres can be concentrated at a specific body location such as in the vicinity of a malignant tumor by applying a magnetic field to the location and then introducing the magnetically attractable microspheres or cells into the circulatory system of the subject. Labeled cells can be separated from a cell mixture by applying a predetermined magnetic field to a tube in which the mixture is flowing. After collection of the labeled cells, the magnetic field is discontinued and the labeled sub-cell population recovered.

Yen, Shiao-Ping S. (Inventor); Rembaum, Alan (Inventor); Molday, Robert S. (Inventor)

1979-01-01

384

Polymeric Anti-HIV Therapeutics.  

PubMed

The scope of this review is to highlight the application of polymer therapeutics in an effort to curb the transmission and infection of the human immunodeficiency virus (HIV). Following a description of the HIV life cycle, the use of approved antiretroviral drugs that inhibit critical steps in the HIV infection process is highlighted. After that, a comprehensive overview of the structure and inhibitory properties of polymeric anti-HIV therapeutic agents is presented. This overview will include inhibitors based on polysaccharides, synthetic polymers, dendritic polymers, polymer conjugates as well as polymeric DC-SIGN antagonists. The review will conclude with a section that discusses the applications of polymers and polymer conjugates as systemic and topical anti-HIV therapeutics. PMID:25185484

Danial, Maarten; Klok, Harm-Anton

2014-09-01

385

Polymeric cationic substituted acrylamide surfactants  

SciTech Connect

A new composition of matter comprises a copolymer of a surface active quaternary ammonium monomer salt and from 50 to 97% by wt of acrylamide. The new copolymers can have molecular weights substantially greater than 10,000 and still remain water soluble and surface active. Copolymers are prepared by polymerization techniques known in the art. The quaternary ammonium monomer is dispersed under inert atmosphere in aqueous solution which may additionally contain dissolved therein a low molecular weight alcohol such as ethanol, isopropanol, and the like. Acidic polymerization initiator such as the azo initiators, organic peroxides, or redox initiators such as the sulfite- persulfate system is then added in an amount calculated to yield a polymer product of desired molecular weight. (14 claims.

Nieh, E.C.Y.

1983-11-15

386

Nanoscale mechanical and tribological properties of fluorocarbon films grafted onto plasma-treated low-density polyethylene surfaces  

NASA Astrophysics Data System (ADS)

Fluorocarbon (FC) films were grafted onto Ar plasma-treated low-density polyethylene (LDPE) surfaces by plasma polymerization and deposition. The evolution of the surface morphology of the grafted FC films was investigated at different scales with an atomic force microscope. Nanoscale sliding experiments performed with a surface force microscope provided insight into the nanotribological properties of Ar plasma-treated LDPE, with and without grafted FC films, in terms of applied normal load and number of sliding cycles. The observed trends are explained in the context of microstructure models accounting for morphological and structure changes at the LDPE surface due to the effects of plasma treatment (e.g., selective etching of amorphous phase, chain crosslinking and FC film grafting) and surface sliding (e.g., crystalline lamellae alignment along the sliding direction). Nanoindentation experiments elucidated the effect of plasma treatment on surface viscoelasticity and global contact stiffness. The results of this study demonstrate that plasma-assisted grafting of FC films is an effective surface modification method for tuning the nanomechanical/tribological properties of polymers.

Cheng, Q.; Komvopoulos, K.

2012-03-01

387

Facile method to prepare smooth and homogeneous polymer brush surfaces of varied brush thickness and grafting density.  

PubMed

This Article describes a facile method to prepare smooth and homogeneous polymer brush surfaces of variable grafting density from a solid surface by combining Langmuir-Blodgett (LB) deposition with surface-initiated atom transfer radical polymerization (SI-ATRP). This method is successfully demonstrated by the preparation of thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) brush surfaces on smooth silicon and quartz substrates. With the custom-synthesized inert diluent whose chemical structure, except end-functionality, is the same as that of the reactive initiator, smooth and chemically homogeneous mixed monolayers of initiators and inert diluents are immobilized on a solid surface by LB deposition, allowing the further variation of the grafting density of PNIPAM brushes grafted from the initiator monolayers of varied initiator coverage. With the optimized molar ratio of deactivator, Cu(II) in the Cu(I)-ligand catalyst complex, the brush thickness of PNIPAM brushes at varied grafting density is controlled to grow nearly linearly with reaction time while smoothness and chemical homogeneity of PNIPAM brushes are achieved. For the demonstrated PNIPAM brush surfaces, the thermoresponsive characteristics of PNIPAM brushes are also verified. This combined LB-ATRP method can be applied to graft a variety of polymer brushes, including polyelectrolytes and block copolymers, from different solid substrates. PMID:19863074

Wang, Shengqin; Zhu, Yingxi

2009-12-01

388

Influence of ischemia before vein grafting on early hyperplasia of the graft and the dynamic changes of the intima after grafting  

PubMed Central

Background To investigate both the influence of ischemia before grafting on early hyperplasia of the vein grafts, and the dynamic changes of the intima after grafting in a rabbit model of vein graft disease. Methods We performed paired vein graft experiments under different ischemic conditions (15 vs. 60 min; 15 vs. 90 min) in the neck of the rabbits and compared the differences between the grafts. Clopidogrel, an anti-platelet agent, was administered before and after surgery. Twenty-eight days after the grafting procedure, the veins were evaluated microscopically. The dynamic changes of the intima after grafting were evaluated by scanning electron microscopy over time. Results The vein grafts subjected to 60- or 90-min ischemia exhibited no differences compared to those subjected to 15-min ischemia in terms of the mean thickness of the intimal, medial, and adventitial layers of the graft. Similarly, there was no difference in the Ki-67 labeling index (proliferation marker) between the vein grafts. Vein grafts with 15-min ischemia lost endothelial cells (ECs) but healed by 3 days post graft, whereas vein grafts with 90-min ischemia suffered serious EC loss, which was restored with new ECs during days 2 to 14 post graft. Conclusions Ninety-minute ischemia before vein grafting can cause serious EC loss, but does not increase early intimal hyperplasia when clopidogrel is administered. Protecting the vein from ischemia and reperfusion injury preserves ECs. PMID:23006637

2012-01-01

389

Design and development of multilayer vascular graft  

NASA Astrophysics Data System (ADS)

Vascular graft is a widely-used medical device for the treatment of vascular diseases such as atherosclerosis and aneurysm as well as for the use of vascular access and pediatric shunt, which are major causes of mortality and morbidity in this world. Dysfunction of vascular grafts often occurs, particularly for grafts with diameter less than 6mm, and is associated with the design of graft materials. Mechanical strength, compliance, permeability, endothelialization and availability are issues of most concern for vascular graft materials. To address these issues, we have designed a biodegradable, compliant graft made of hybrid multilayer by combining an intimal equivalent, electrospun heparin-impregnated poly-epsilon-caprolactone nanofibers, with a medial equivalent, a crosslinked collagen-chitosan-based gel scaffold. The intimal equivalent is designed to build mechanical strength and stability suitable for in vivo grafting and to prevent thrombosis. The medial equivalent is designed to serve as a scaffold for the activity of the smooth muscle cells important for vascular healing and regeneration. Our results have shown that genipin is a biocompatible crosslinker to enhance the mechanical properties of collagen-chitosan based scaffolds, and the degradation time and the activity of smooth muscle cells in the scaffold can be modulated by the crosslinking degree. For vascular grafting and regeneration in vivo, an important design parameter of the hybrid multilayer is the interface adhesion between the intimal and medial equivalents. With diametrically opposite affinities to water, delamination of the two layers occurs. Physical or chemical modification techniques were thus used to enhance the adhesion. Microscopic examination and graft-relevant functional characterizations have been performed to evaluate these techniques. Results from characterization of microstructure and functional properties, including burst strength, compliance, water permeability and suture strength, showed that the multilayer graft possessed properties mimicking those of native vessels. Achieving these FDA-required functional properties is essential because they play critical roles in graft performances in vivo such as thrombus formation, occlusion, healing, and bleeding. In addition, cell studies and animal studies have been performed on the multilayer graft. Our results show that the multilayer graft support mimetic vascular culture of cells and the acellular graft serves as an artery equivalent in vivo to sustain the physiological conditions and promote appropriate cellular activity. In conclusion, the newly-developed hybrid multilayer graft provides a proper balance of biomechanical and biochemical properties and demonstrates the potential for the use of vascular tissue engineering and regeneration.

Madhavan, Krishna

2011-07-01

390

Use of free radicals on the surface of plasma polymer for the initiation of a polymerization reaction.  

PubMed

A novel approach to functionalize plasma polymer films (PPFs) through the grafting polymerization initiated from free radicals trapped in the film was developed in this work. 2-Ethylhexyl acrylate (EHA) was chosen as radically polymerizable monomer given the wide use of its corresponding polymer in coating and adhesive applications. The occurrence of the grafting was first confirmed by time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). Then grafted chains were studied in more detail. The thickness of grafted chains was quantitatively estimated by angle-resolved XPS (ARXPS), while their morphology and interfacial behavior were qualitatively investigated by atomic force microscopy (AFM), contact angle measurements, and quartz crystal microbalance (QCM). The latter technique provided additional insights regarding the swelling behavior of the grafted layer and its stability upon exposure to challenging environments. Reported scientific findings suggest to use this approach for the covalent binding of a very thin layer on the top surface of a PPF without affecting its bulk properties. PMID:24143897

Khelifa, Farid; Ershov, Sergey; Habibi, Youssef; Snyders, Rony; Dubois, Philippe

2013-11-27

391

Microwave induced synthesis of graft copolymer of binary vinyl monomer mixtures onto delignified Grewia optiva fiber: application in dye removal.  

PubMed

Grafting method, through microwave radiation technique is very effective in terms of time consumption, cost effectiveness and environmental friendliness. Via this method, delignified Grewia optiva identified as a waste biomass, was graft copolymerized with methylmethacrylate (MMA) as an principal monomer in a binary mixture of ethyl methacrylate (EMA) and ethyl acrylate (EA) under microwave irradiation (MWR) using ascorbic acid/H2O2 as an initiator system. The concentration of the comonomer was optimized to maximize the graft yield with respect to the primary monomer. Maximum graft yield (86.32%) was found for dGo-poly(MMA-co-EA) binary mixture as compared to other synthesized copolymer. The experimental results inferred that the optimal concentrations for the comonomers to the optimized primary monomer was observed to be 3.19 mol/L × 10(-1) for EMA and 2.76 mol/L × 10(-1) for EA. Delignified and graft copolymerized fiber were subjected to evaluation of physicochemical properties such as swelling behavior and chemical resistance. The synthesized graft copolymers were characterized with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and X-ray diffraction techniques. Thermal stability of dGo-poly(MMA-co-EA) was found to be more as compared to the delignified Grewia optiva fiber and other graft copolymers. Although the grafting technique was found to decrease percentage crystallinity and crystallinity index among the graft copolymers but there was significant increase in their acid/base and thermal resistance properties. The grafted samples have been explored for the adsorption of hazardous methylene dye from aqueous system. PMID:25157348

Gupta, Vinod Kumar; Pathania, Deepak; Priya, Bhanu; Singha, Amar Singh; Sharma, Gaurav

2014-01-01

392

Grafted methylenediphosphonate ion exchange resins  

DOEpatents

An ion exchange resin is disclosed that is comprised of an insoluble copolymer onto which are grafted pendent groups that provide 1.0 to about 10 mmol/g dry weight phosphorous. The pendent groups have the formula ##STR1## wherein R is hydrogen, a cation or mixtures thereof; and R.sup.1 is hydrogen or an C.sub.1 -C.sub.2 alkyl group. The resin also contains zero to about 5 mmol/g dry weight of pendent aromatic sulfonate groups. Processes for making and using an ion exchange-resin are also disclosed.

Trochimcznk, Andrzej W. (Knoxville, TN); Gatrone, Ralph C. (Plymouth, PA); Alexandratos, Spiro (Knoxville, TN); Horwitz, E. Philip (Naperville, IL)

1998-01-27

393

Grafted methylenediphosphonate ion exchange resins  

DOEpatents

An ion exchange resin is disclosed that is comprised of an insoluble copolymer onto which are grafted pendent groups that provide 1.0 to about 10 mmol/g dry weight phosphorus. The pendent groups have the formula as shown in the patent wherein R is hydrogen, a cation or mixtures thereof; and R{sup 1} is hydrogen or an C{sub 1}-C{sub 2} alkyl group. The resin also contains zero to about 5 mmol/g dry weight of pendent aromatic sulfonate groups. Processes for making and using an ion exchange resin are also disclosed.

Trochimcznk, A.W.; Gatrone, R.C.; Alexandratos, S.; Horwitz, E.P.

1997-04-08

394

Grafted methylenediphosphonate ion exchange resins  

DOEpatents

An ion exchange resin is disclosed that is comprised of an insoluble copolymer onto which are grafted pendent groups that provide 1.0 to about 10 mmol/g dry weight phosphorous. The pendent groups have the formula ##STR1## wherein R is hydrogen, a cation or mixtures thereof; and R.sup.1 is hydrogen or an C.sub.1 -C.sub.2 alkyl group. The resin also contains zero to about 5 mmol/g dry weight of pendent aromatic sulfonate groups. Processes for making and using an ion exchange resin are also disclosed.

Trochimcznk, Andrzej W. (Knoxbille, TN); Gatrone, Ralph C. (Plymouth, PA); Alexandratos, Spiro (Knoxville, TN); Horwitz, E. Philip (Naperville, IL)

1997-01-01

395

Xenon Treatment Protects Against Cold Ischemia Associated Delayed Graft Function and Prolongs Graft Survival in Rats  

PubMed Central

Prolonged hypothermic storage causes ischemia-reperfusion injury (IRI) in the renal graft, which is considered to contribute to the occurrence of the delayed graft function (DGF) and chronic graft failure. Strategies are required to protect the graft and to prolong renal graft survival. We demonstrated that xenon exposure to human proximal tubular cells (HK-2) led to activation of range of protective proteins. Xenon treatment prior to or after hypothermia–hypoxia challenge stabilized the HK-2 cellular structure, diminished cytoplasmic translocation of high-mobility group box (HMGB) 1 and suppressed NF-?B activation. In the syngeneic Lewis-to-Lewis rat model of kidney transplantation, xenon exposure to donors before graft retrieval or to recipients after engraftment decreased caspase-3 expression, localized HMGB-1 within nuclei and prevented TLR-4/NF-?B activation in tubular cells; serum pro-inflammatory cytokines IL-1?, IL-6 and TNF-? were reduced and renal function was preserved. Xenon treatment of graft donors or of recipients prolonged renal graft survival following IRI in both Lewis-to-Lewis isografts and Fischer-to-Lewis allografts. Xenon induced cell survival or graft functional recovery was abolished by HIF-1? siRNA. Our data suggest that xenon treatment attenuates DGF and enhances graft survival. This approach could be translated into clinical practice leading to a considerable improvement in long-term graft survival. PMID:23710625

Zhao, H; Watts, H R; Chong, M; Huang, H; Tralau-Stewart, C; Maxwell, P H; Maze, M; George, A J T; Ma, D

2013-01-01

396

Subcutaneous polymeric matrix system p(HEMA-BGA) for controlled release of an anticancer drug (5-fluorouracil). II: Release kinetics.  

PubMed

A subcutaneous polymeric drug delivery system, which consists of a polymeric matrix of poly(hydroxyethyl methacrylate-bisglycol acrylate), was developed. 5-fluorouracil was used as the model anticancer drug. Polymer-drug beads with a diameter of 3 mm were prepared by low-temperature radiation polymerization. In order to modify the release rate, polymeric beads with different composition, drug loading and crosslinking density were obtained. The kinetics of drug release were described by the expression Mt/M infinity = ktn. The diffusional release exponent 'n', which was calculated from the release curves, indicated that the mechanism of drug release from the polymeric matrix is due to the anomalous (non-Fickian) type of diffusion. PMID:3214661

Denizli, A; Kiremitçi, M; Pi?kin, E

1988-07-01

397

All-Inside Anterior Cruciate Ligament Graft Link: Graft Preparation Technique  

PubMed Central

The anatomic single-bundle, all-inside anterior cruciate ligament graft-link technique requires meticulous graft preparation. The graft choice is no-incision allograft or gracilis-sparing, posterior semitendinosus autograft. The graft is linked, like a chain, to femoral and tibial TightRope cortical suspensory fixation devices with adjustable-length graft loops (Arthrex, Naples, FL) in the following manner: the graft is quadrupled, and the free ends are first whip-stitched and then sutured with a buried-knot technique, 4 times through each strand in a loop. The graft is placed on a tensioning station under approximately 20 lb of tension during arthroscopic preparation of the knee and then removed from the tensioner and inserted into all-inside femoral and tibial sockets through the anteromedial arthroscopic portal. PMID:23766990

Lubowitz, James H.

2012-01-01

398

Silent Infection in Clotted Hemodialysis Access Grafts  

Microsoft Academic Search

Thrombotic and infectious complications are fre- quent causes of hemodialysis vascular access failure and con- tribute considerably to the cost of care for chronic hemodial- ysis patients. Although there is clear indication for removal of patent grafts in unresolved bacteremia, there are no guidelines for the management of clotted nonfunctioning grafts. To eval- uate for the existence and clinical relevance

J. CARLOS AYUS; DAVID SHEIKH-HAMAD

399

Aortoesophageal fistula after thoracic stent grafting.  

PubMed

Aortoesophageal fistula after thoracic stent grafting is rare and usually fatal. A 66-year-old woman developed an aortoesophageal fistula 1 month after endovascular stent grafting of the thoracic aorta for a complicated type B dissection. She had a fatal episode of massive bleeding before she could be treated. The limited treatment options are discussed. PMID:22100932

Albors, José; Bahamonde, José Ángel; Sanchis, Juan Manuel; Boix, Ricardo; Palmero, Julio

2011-10-01

400

Emerging concepts in liver graft preservation  

PubMed Central

The urgent need to expand the donor pool in order to attend to the growing demand for liver transplantation has obliged physicians to consider the use of suboptimal liver grafts and also to redefine the preservation strategies. This review examines the different methods of liver graft preservation, focusing on the latest advances in both static cold storage and machine perfusion (MP). The new strategies for static cold storage are mainly designed to increase the fatty liver graft preservation via the supplementation of commercial organ preservation solutions with additives. In this paper we stress the importance of carrying out effective graft washout after static cold preservation, and present a detailed discussion of the future perspectives for dynamic graft preservation using MP at different temperatures (hypothermia at 4?°C, normothermia at 37?°C and subnormothermia at 20?°C-25?°C). Finally, we highlight some emerging applications of regenerative medicine in liver graft preservation. In conclusion, this review discusses the “state of the art” and future perspectives in static and dynamic liver graft preservation in order to improve graft viability. PMID:25593455

Bejaoui, Mohamed; Pantazi, Eirini; Folch-Puy, Emma; Baptista, Pedro M; García-Gil, Agustín; Adam, René; Roselló-Catafau, Joan

2015-01-01

401

Starch Graft Copolymers: Novel Applications in Industry  

Microsoft Academic Search

Starch, which is a natural carbohydrate biopolymer, has been the subject of academic and industrial studies for many decades, basically due to its low cost, biodegradability and versatility of use. Chemical modification of starch by grafting various monomers onto it imparts increased hydrophilicity, hydrophobicity or polyelectrolyte nature to starch depending on the reagent and conditions used. The starch graft copolymers

A. N. Jyothi

2010-01-01

402

Emerging concepts in liver graft preservation.  

PubMed

The urgent need to expand the donor pool in order to attend to the growing demand for liver transplantation has obliged physicians to consider the use of suboptimal liver grafts and also to redefine the preservation strategies. This review examines the different methods of liver graft preservation, focusing on the latest advances in both static cold storage and machine perfusion (MP). The new strategies for static cold storage are mainly designed to increase the fatty liver graft preservation via the supplementation of commercial organ preservation solutions with additives. In this paper we stress the importance of carrying out effective graft washout after static cold preservation, and present a detailed discussion of the future perspectives for dynamic graft preservation using MP at different temperatures (hypothermia at 4?°C, normothermia at 37?°C and subnormothermia at 20?°C-25?°C). Finally, we highlight some emerging applications of regenerative medicine in liver graft preservation. In conclusion, this review discusses the "state of the art" and future perspectives in static and dynamic liver graft preservation in order to improve graft viability. PMID:25593455

Bejaoui, Mohamed; Pantazi, Eirini; Folch-Puy, Emma; Baptista, Pedro M; García-Gil, Agustín; Adam, René; Roselló-Catafau, Joan

2015-01-14

403

Ring-expansion metathesis polymerization: catalyst-dependent polymerization profiles.  

PubMed

Ring-expansion metathesis polymerization (REMP) mediated by recently developed cyclic Ru catalysts has been studied in detail with a focus on the polymer products obtained under varied reaction conditions and catalyst architectures. Depending upon the nature of the catalyst structure, two distinct molecular weight evolutions were observed. Polymerization conducted with catalysts bearing six-carbon tethers displayed rapid polymer molecular weight growth which reached a maximum value at ca. 70% monomer conversion, resembling a chain-growth polymerization mechanism. In contrast, five-carbon-tethered catalysts led to molecular weight growth that resembled a step-growth mechanism with a steep increase occurring only after 95% monomer conversion. The underlying reason for these mechanistic differences appeared to be ready release of five-carbon-tethered catalysts from growing polymer rings, which competed significantly with propagation. Owing to reversible chain transfer and the lack of end groups in REMP, the final molecular weights of cyclic polymers was controlled by thermodynamic equilibria. Large ring sizes in the range of 60-120 kDa were observed at equilibrium for polycyclooctene and polycyclododecatriene, which were found to be independent of catalyst structure and initial monomer/catalyst ratio. While six-carbon-tethered catalysts were slowly incorporated into the formed cyclic polymer, the incorporation of five-carbon-tethered catalysts was minimal, as revealed by ICP-MS. Further polymer analysis was conducted using melt-state magic-angle spinning (13)C NMR spectroscopy of both linear and cyclic polymers, which revealed little or no chain ends for the latter topology. PMID:19199611

Xia, Yan; Boydston, Andrew J; Yao, Yefeng; Kornfield, Julia A; Gorodetskaya, Irina A; Spiess, Hans W; Grubbs, Robert H

2009-02-25

404

Structural insights into de novo actin polymerization  

PubMed Central

Summary Many cellular functions depend on rapid and localized actin polymerization/depolymerization. Yet, the de novo polymerization of actin in cells is kinetically unfavorable because of the instability of polymerization intermediates (small actin oligomers) and the actions of actin monomer binding proteins. Cells use filament nucleation and elongation factors to initiate and sustain polymerization. Structural biology is beginning to shed light on the diverse mechanisms by which these unrelated proteins initiate polymerization, undergo regulation, and mediate the transition of monomeric actin onto actin filaments. A prominent role is played by the W domain, which in some of these proteins occurs in tandem repeats that recruit multiple actin subunits. Pro-rich regions are also abundant and mediate the binding of profilin-actin complexes, which are the main source of polymerization competent actin in cells. Filament nucleation and elongation factors frequently interact with Rho family GTPases, which relay signals from membrane receptors to regulate actin cytoskeleton remodeling. PMID:20096561

Dominguez, Roberto

2010-01-01

405

Dermis fat graft in eviscerated sockets.  

PubMed

Following evisceration, three patients who experienced extrusion of synthetic orbital implant underwent socket reconstruction using an autogenous dermis fat graft. An incision into the fundus of the existing sclera was necessary to provide for an adequate vascular bed for a composite fat graft, although the anterior ring of existing sclera with extraocular muscle attachments was not disturbed. Conjunctival reepithelialization of the dermal surface and enhancement of orbital volume occurred in each case. Furthermore, the autogenous fat graft retained the original excellent globe motility that was present before the socket reconstruction. After an average follow-up of 18 months, the volume restoration, integrity of conjunctival epithelium and fornices, and the graft viability have remained unchanged. As with alloplastic orbital implant extrusions in enucleated sockets, autogeneous dermis fat grafts can be useful in managing extrusions in previously eviscerated sockets. PMID:2487209

Borodic, G E; Townsend, D J; Beyer-Machule, C K

1989-01-01

406

Graft healing in anterior cruciate ligament reconstruction  

PubMed Central

Successful anterior cruciate ligament reconstruction with a tendon graft necessitates solid healing of the tendon graft in the bone tunnel. Improvement of graft healing to bone is crucial for facilitating an early and aggressive rehabilitation and ensuring rapid return to pre-injury levels activity. Tendon graft healing in a bone tunnel requires bone ingrowth into the tendon. Indirect Sharpey fiber formation and direct fibrocartilage fixation confer different anchorage strength and interface properties at the tendon-bone interface. For enhancing tendon graft-to-bone healing, we introduce a strategy that includes the use of periosteum, hydrogel supplemented with periosteal progenitor cells and bone morphogenetic protein-2, and a periosteal progenitor cell sheet. Future studies include the use of cytokines, gene therapy, stem cells, platelet-rich plasma, and mechanical stress for tendon-to-bone healing. These strategies are currently under investigation, and will be applied in the clinical setting in the near future. PMID:19772670

Chen, Chih-Hwa

2009-01-01

407

Voltage-tunable volume transitions in nanoscale films of poly(hydroxyethyl methacrylate) surfaces grafted onto gold.  

PubMed

Surface grafting of a polymerizable monomer onto Au was used to produce nanometer-scale planar hydrogel films with controllable volume. A self-assembled monolayer of 11-mercaptoundecanoic acid on a planar Au surface was activated through water-soluble carbodiimide and N-hyroxysuccinimide followed by reaction with 2-aminomethacrylate to produce a methacrylate-terminated surface layer, which readily polymerized under UV radiation in the presence of hydroxyethyl methacrylate monomer, ethylene glycol dimethacrylate cross-linker, and a photoinitiator. The reaction steps were characterized by external reflection mode Fourier transform IR spectroscopy. Under controlled UV exposure, thin (3 nm < d < 10 nm) hydrogel films were obtained from 1:1 ethanol/H(2)O. Surface plasmon resonance measurements were used to characterize both the synthesis of the hydrogel and the potential-induced volume changes. The nanometer-scale hydrogels thus produced undergo reproducible changes in thickness, when a potential is applied across the film. Thickness changes increasing with applied potential were obtained for both voltages in the range |V(appl)|

Lokuge, Ishika S; Bohn, Paul W

2005-03-01

408

[Autologous fat grafting and rhinoplasty].  

PubMed

Revision rhinoplasty can be very challenging especially in cases of thin skin. Autologous fat graft is utilized in numerous applications in plastic surgery; however, its use relative to the nasal region remains uncommon. Adipose tissue, by virtue of its volumetric qualities and its action on skin trophicity, can be considered to be a gold standard implant. From 2006 until 2012, we have treated patients by lipofilling in order to correct sequelae of rhinoplasty. The mean quantity of adipose tissue injected was 2.1cm(3) depending on the importance of the deformity and the area of injection: irregularity of the nasal dorsum, visible lateral osteotomies, saddle nose. Following the course of our practice, we conceived micro-cannulas that allow a much greater accuracy in the placement of the graft and enable to perform interventions under local anesthesia. These non-traumatic micro-cannulas do not cause post-operative ecchymosis and swelling which shorten the recovery time for the patient. On patients who have undergone multiple operations, lipofilling can be a simple and reliable alternative to correct imperfections that may take place after a rhinoplasty. PMID:24997796

Nguyen, P S; Baptista, C; Casanova, D; Bardot, J; Magalon, G

2014-12-01

409

Vibrational and electronic characterization of ethynyl derivatives grafted onto hydrogenated Si(111) surfaces.  

PubMed

Covalent grafting of ethynyl derivatives (-C triple bond C-H, -C triple bond C-CH3, -C triple bond C-aryl) onto H-terminated Si(111) surfaces was performed by a one-step anodic treatment in Grignard electrolytes. The electrochemical grafting of such ethynyl derivatives, which tends to form ultrathin polymeric layers, can be controlled by the current and charge flow passing through the Si electrode. The prepared ultrathin layers cover the Si surface and had a thickness up to 20 nm, as investigated by the scanning electron microscopy (SEM) technique. Exchanging Cl for Br in the ethynyl Grignard reagent leads to very thin layers, even under the same electrochemical conditions. However, for all ethynyl derivatives, high-resolution synchrotron X-ray photoelectron spectroscopy (SXPS) investigations reveal the incorporation of halogen atoms in the organic layers obtained. Moreover, it was observed that the larger the end group of the ethynyl derivative, the thinner the thickness of the ultrathin polymeric layers as measured by both SXPS and SEM techniques after low and high current flow respectively. For the first time, these new types of ultrathin organic layers on Si surfaces were investigated using infrared spectroscopic ellipsometry (IRSE). The different possible reaction pathways are discussed. PMID:19601568

Yang, F; Hunger, R; Roodenko, K; Hinrichs, K; Rademann, K; Rappich, J

2009-08-18

410

Solvent effect on post-irradiation grafting of styrene onto poly(ethylene-alt-tetrafluoroethylene) (ETFE) films  

NASA Astrophysics Data System (ADS)

Radiation-induced grafting of styrene onto ETFE films in different solvent was investigated after simultaneous irradiation (in post-irradiation condition) using a 60Co source. Grafting of styrene followed by sulfonation onto poly(ethylene-alt-tetrafluoroethylene) (ETFE) are currently studied for synthesis of ion exchange membranes. The ETFE films were immersed in styrene/toluene, styrene/methanol and styrene/isopropyl alcohol and irradiated at 20 and 100 kGy doses at room temperature. The post-irradiation time was established at 14 day and the grafting degree was evaluated. The grafted films were sulfonated using chlorosulfonic acid and 1,2-dichloroethane 20:80 (v/v) at room temperature for 5 h. The degree of grafting (DOG) was determined gravimetrically and physical or chemical changes were evaluated by differential scanning calorimeter analysis (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The ion exchange capacity (IEC) values showed the best performance of sulfonation for ETFE membranes grafted in toluene solvent. Surface images of the grafted films by SEM technique have presented a strong effect of the solvents on the films morphology.

Napoleão Geraldes, Adriana; Augusto Zen, Heloísa; Ribeiro, Geise; Fernandes Parra, Duclerc; Benévolo Lugão, Ademar

2013-03-01

411

UV-Triggered Dopamine Polymerization: Control of Polymerization, Surface Coating, and Photopatterning.  

PubMed

UV irradiation is demonstrated to initiate dopamine polymerization and deposition on different surfaces under both acidic and basic pH. The observed acceleration of the dopamine polymerization is explained by the UV-induced formation of reactive oxygen species that trigger dopamine polymerization. The UV-induced dopamine polymerization leads to a better control over polydopamine deposition and formation of functional polydopamine micropatterns. PMID:25381870

Du, Xin; Li, Linxian; Li, Junsheng; Yang, Chengwu; Frenkel, Nataliya; Welle, Alexander; Heissler, Stefan; Nefedov, Alexei; Grunze, Michael; Levkin, Pavel A

2014-12-01

412

POLYMER PROGRAM SEMINAR "Targeted polymeric nanoparticles  

E-print Network

systems are polymeric nanoparticles and liposomes. Controlled release polymer technology impacts every drugs for combination therapy. The surface engineering of these nanoparticles may yield them "stealth

Alpay, S. Pamir

413

Functionalized carbon nanotube via distillation precipitation polymerization and its application in nafion-based composite membranes.  

PubMed

The objective of this study is to develop a novel approach to in situ functionalizing multiwalled carbon nanotubes (MWCNTs) and exploring their application in Nafion-based composite membranes for efficient proton conduction. Covalent grafting of acrylate-modified MWCNTs with poly(methacrylic acid-co-ethylene glycol dimethacrylate), poly(vinylphosphonic acid-co-ethylene glycol dimethacrylate), and sulfonated poly(styrene-co-divinylbenzene) was achieved via surface-initiated distillation precipitation polymerization. The formation of core-shell structure was verified by TEM images, and polymer layers with thickness around 30 nm were uniformly covered on the MWCNTs. The graft yield reached up to 93.3 wt % after 80 min of polymerization. The functionalized CNTs (FCNTs) were incorporated into the Nafion matrix to prepare composite membranes. The influence of various functional groups (-COOH, -PO3H2, and -SO3H) in FCNTs on proton transport of the composite membranes was studied. The incorporation of FCNTs afforded the composite membranes significantly enhanced proton conductivities under reduced relative humidity. The composite membrane containing 5 wt % phosphorylated MWCNTs (PCNTs) showed the highest proton conductivity, which was attributed to the construction of lower-energy-barrier proton transport pathways by PCNTs, and excellent water-retention and proton-conduction properties of the cross-linked polymer in PCNTs. Moreover, the composite membranes exhibited an enhanced mechanical stability. PMID:25109828

He, Guangwei; Zhao, Jing; Hu, Shen; Li, Lingqiao; Li, Zongyu; Li, Yifan; Li, Zhen; Wu, Hong; Yang, Xinlin; Jiang, Zhongyi

2014-09-10

414

Tailored covalent grafting of hexafluoropropylene oxide oligomers onto silica nanoparticles: toward thermally stable, hydrophobic, and oleophobic nanocomposites.  

PubMed

The modification of silica nanoparticles with hexafluoropropylene oxide (HFPO) oligomers has been investigated. HFPO oligomers with two different average degrees of polymerization (DPn = 8 and 15) were first prepared by anionic ring-opening polymerization, deactivated by methanol, and in some cases postfunctionalized by aminopropyl(tri)ethoxysilane or allylamine. The "grafting onto" reactions of these oligomers were then carried out either on bare silica (reaction between a silanol surface and ethoxy-silanized HFPO) or on silica functionalized by amino groups (in an amidation reaction with methyl ester-ended HFPO) or mercapto groups (via the radical addition of allyl-functionalized HFPO). Hybrid nanoparticles thus obtained were characterized by solid-state (29)Si NMR and FTIR spectroscopies as well as elemental and thermogravimetric analyses. The results assessed a significant yield of covalent grafting of HFPO oligomers when performing the hydrolysis-condensation of ethoxylated HFPO on the bare silica surface, compared to the other two methods that merely led to physically adsorbed HFPO chains. Chemically grafted nanohybrids showed a high thermal stability (up to 400 °C) as well as a very low surface tension (typically 5 mN/m) compared to physisorbed complexes. PMID:21391662

Durand, Nelly; Mariot, David; Améduri, Bruno; Boutevin, Bernard; Ganachaud, François

2011-04-01

415

Correction of short nose deformity using a septal extension graft combined with a derotation graft.  

PubMed

In patients having a short nose with a short septal length and/or severe columellar retraction, a septal extension graft is a good solution, as it allows the dome to move caudally and pushes down the columellar base. Fixing the medial crura of the alar cartilages to a septal extension graft leads to an uncomfortably rigid nasal tip and columella, and results in unnatural facial animation. Further, because of the relatively small and weak septal cartilage in the East Asian population, undercorrection of a short nose is not uncommon. To overcome these shortcomings, we have used the septal extension graft combined with a derotation graft. Among 113 patients who underwent the combined procedure, 82 patients had a short nose deformity alone; the remaining 31 patients had a short nose with columellar retraction. Thirty-two patients complained of nasal tip stiffness caused by a septal extension graft from previous operations. In addition to the septal extension graft, a derotation graft was used for bridging the gap between the alar cartilages and the septal extension graft for tip lengthening. Satisfactory results were obtained in 102 (90%) patients. Eleven (10%) patients required revision surgery. This combination method is a good surgical option for patients who have a short nose with small septal cartilages and do not have sufficient cartilage for tip lengthening by using a septal extension graft alone. It can also overcome the postoperative nasal tip rigidity of a septal extension graft. PMID:24511489

Paik, Moo Hyun; Chu, Lo Shui

2014-01-01

416

Development of Initiation Strategies for the Optimization and Stabilization of Brushes Formed by Surface-Initiated Radical Polymerization  

NASA Astrophysics Data System (ADS)

Three challenges facing the continued development of the surface-initiated (SI) polymerization field are addressed. The first challenge is that surface-initiated free radical polymerization (SI-FRP) is currently under-represented in literature reports, despite the fact that SI-FRP offers several important advantages over surface-initiated controlled radical polymerization (SI-CRP) and represents a complementary approach. Recognizing that simple, efficient, and safer approaches to synthesizing effective surface free radical initiators are needed, we present a novel synthetic route to an azo type free radical initiator that forms self-assembled monolayers on oxide coated surfaces such as silicon and glass. The yield of the novel synthetic approach is approximately double that of the previous method, and the usage of cyanide is reduced dramatically. We characterize the decomposition kinetics of the initiator using differential scanning calorimetry, comparing it with other similar initiators. We characterize the surface properties of initiator layers on silicon using ellipsometry, water contact angle measurements, and x-ray photoelectron spectroscopy (XPS). We demonstrate the use of the initiator for SI-FRP as well as SI-CRP mechanisms including reverse atom transfer radical polymerization (RATRP) and reversible addition-fragmentation transfer (RAFT) polymerization. A second challenge facing the field of SI polymerization involves the stability of grafted polymer brushes in aqueous environments and under tension, both of which are commonly encountered in many applications. We hypothesize that the mechanism of brush degrafting involves hydrolysis of ester backbone units in the initiator, which are ubiquitous in surface-bound polymerization initiator systems. The novel initiator described herein is unique in that its backbone consists of a chemically stable alkane chain, free of esters or other easily hydrolysable groups. We present results of experiments demonstrating the stability of polymer brushes formed from the novel initiator compared against brushes formed from ester-based initiators. The ester-free brushes are found to be more stable under a variety of conditions including p-toluenesulfonic acid, which is commonly used to cleave grafted polymers for analysis, as well in as aqueous systems at low, high, and neutral pH. Therefore the novel initiator constitutes a helpful contribution to the problem of brush stability. The third challenge addressed herein concerns the need for a more robust understanding of SI polymerization mechanisms and their effect on resultant polymer properties. SI polymerizations often differ significantly from corresponding bulk processes due to confinement effects. We conduct a detailed study of the thickness of polystyrene brushes formed by SI-FRP as a function of temperature and initiator conversion. These results are compared against computer simulations of bulk FRP conducted using Gillespie's stochastic simulation algorithm (GSSA). The Arrhenius behavior of the brush thickness is found to deviate significantly from that expected for bulk polymerization due to a two-dimensional Trommsdorff effect in the brush layer. We investigate the strengths and weaknesses of GSSA applied to radical polymerizations in bulk and under confinement, suggesting ideas for improving the accuracy of SI polymerization models. Furthermore, the conditions necessary for free and controlled radical polymerizations are investigated. We describe efforts to achieve SI-CRP by physical means, without chemical additives, using microwave irradiation of conductive substrates. We analyze the heat transfer from microwave absorbing substrates mathematically and we employ a modified CSSA algorithm to gain further insight into the parameter space affecting control over molecular weight and molecular weight distribution in radical polymerization.

Bain, Erich D.

417

Ionene modified small polymeric beads  

NASA Technical Reports Server (NTRS)

Linear ionene polyquaternary cationic polymeric segments are bonded by means of the Menshutkin reaction (quaternization) to biocompatible, extremely small, porous particles containing halide or tertiary amine sites which are centers for attachment of the segments. The modified beads in the form of emulsions or suspensions offer a large, positively-charged surface area capable of irreversibly binding polyanions such as heparin, DNA, RNA or bile acids to remove them from solution or of reversibly binding monoanions such as penicillin, pesticides, sex attractants and the like for slow release from the suspension.

Rembaum, Alan (Inventor)

1977-01-01

418

Marketing NASA Langley Polymeric Materials  

NASA Technical Reports Server (NTRS)

A marketing tool was created to expand the knowledge of LaRC developed polymeric materials, in order to facilitate the technology transfer process and increase technology commercialization awareness among a non-technical audience. The created brochure features four materials, LaRC-CP, LaRC-RP46, LaRC-SI, and LaRC-IA, and highlights their competitive strengths in potential commercial applications. Excellent opportunities exist in the $40 million per year microelectronics market and the $6 billion adhesives market. It is hoped that the created brochure will generate inquiries regarding the use of the above materials in markets such as these.

Flynn, Diane M.

1995-01-01

419

Electrically controlled polymeric gel actuators  

DOEpatents

Electrically controlled polymeric gel actuators or synthetic muscles are described capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots. 11 figures.

Adolf, D.B.; Shahinpoor, M.; Segalman, D.J.; Witkowski, W.R.

1993-10-05

420

Coating of calcia-doped ceria with amorphous silica shell by seeded polymerization technique  

Microsoft Academic Search

Calcia-doped ceria is of potential interest as an ultraviolet (UV) radiation blocking material in personal care products. However, its high catalytic ability for oxidation of organic materials makes it difficult to use as a sunscreen material. Therefore, calcia-doped ceria was coated with amorphous silica by means of seeded polymerization technique in order to depress its oxidation catalytic ability. The catalytic

Ahmed Mohamed. El-Toni; Shu Yin; Shinryo Yabe; Tsugio Sato

2005-01-01

421

Synthesis and silica coating of calcia-doped ceria\\/mica nanocomposite by seeded polymerization technique  

Microsoft Academic Search

Calcia-doped ceria is of potential interest as an ultraviolet (UV) radiation blocking material in personal care products because of the excellent UV light absorption property and low catalytic ability for the oxidation of organic materials superior to undoped ceria. In order to reduce the oxidation catalytic activity further, calcia-doped ceria was coated with amorphous silica by means of seeded polymerization

Ahmed Mohamed El-Toni; Shu Yin; Tsugio Sato

2006-01-01

422

Vascularized bone grafts for the management of skeletal defects in orthopaedic trauma and reconstructive surgery.  

PubMed

Bone loss from trauma, neoplasia, reconstructive surgery and congenital defects remains a major health problem. The long-term clinical goal is to reconstruct bony tissue in an anatomically functional three-dimensional morphology. In the extremities, bone grafts are used for the treatment of non-unions and necrotic lesions, for skeletal structural support and for the reconstruction of defects resulting from trauma, tumor excision, osteomyelitis, congenital pseudarthrosis, or radiation necrosis. In all cases their use is successful provided that the host bed has adequate vascularization. In cases of decreased blood supply, a vascularized bone graft should be applied. The intrinsic blood supply of the vascularized bone grafts leads to higher success rates and to acceleration of the repair process in the reconstruction of defects and necrotic lesions of the skeleton. PMID:23351876

Soucacos, Panayotis N; Kokkalis, Zinon T; Piagkou, Mara; Johnson, Elizabeth O

2013-01-01

423

Post-Polymerization Crosslinked Polyurethane Shape-Memory Polymers  

PubMed Central

Novel urethane shape-memory polymers (SMPs) of significant industrial relevance have been synthesized and characterized. Chemically crosslinked SMPs have traditionally been made in a one-step polymerization of monomers and crosslinking agents. However, these new post-polymerization crosslinked SMPs can be processed into complex shapes by thermoplastic manufacturing methods and later crosslinked by heat exposure or by electron beam irradiation. Several series of linear, olefinic urethane polymers were made from 2-butene-1,4-diol, other saturated diols, and various aliphatic diisocyanates. These thermoplastics were melt-processed into desired geometries and thermally crosslinked at 200°C or radiation crosslinked at 50 kGy. The SMPs were characterized by solvent swelling and extraction, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile testing, and qualitative shape-recovery analysis. Swelling and DMA results provided concrete evidence of chemical crosslinking, and further characterization revealed that the urethanes had outstanding mechanical properties. Key properties include tailorable transitions between 25 and 80°C, tailorable rubbery moduli between 0.2 and 4.2 MPa, recoverable strains approaching 100%, failure strains of over 500% at Tg, and qualitative shape-recovery times of less than 12 seconds at body temperature (37°C). Because of its outstanding thermo-mechanical properties, one polyurethane was selected for implementation in the design of a complex medical device. These post-polymerization crosslinked urethane SMPs are an industrially relevant class of highly processable shape-memory materials. PMID:21572577

Hearon, K.; Gall, K.; Ware, T.; Maitland, D. J.; Bearinger, J. P.; Wilson, T. S.

2011-01-01

424

From interfacial ring-opening polymerization to melt processing of cellulose nanowhisker-filled polylactide-based nanocomposites.  

PubMed

In the present work, cellulose nanowhiskers (CNWs), extracted from ramie fibers, were incorporated in polylactide (PLA)-based composites. Prior to the blending, PLA chains were chemically grafted on the surface of CNW to enhance the compatibilization between CNW and the hydrophobic polyester matrix. Ring-opening polymerization of l-lactide was initiated from the hydroxyl groups available at the CNW surface to yield CNW-g-PLA nanohybrids. PLA-based nanocomposites were prepared by melt blending to ensure a green concept of the study thereby limiting the use of organic solvents. The influence of PLA-grafted cellulose nanoparticles on the mechanical and thermal properties of the ensuing nanocomposites was deeply investigated. The thermal behavior and mechanical properties of the nanocomposites were determined using differential scanning calorimetry (DSC) and dynamical mechanical and thermal analysis (DMTA), respectively. It was clearly evidenced that the chemical grafting of CNW enhances their compatibility with the polymeric matrix and thus improves the final properties of the nanocomposites. Large modification of the crystalline properties such as the crystallization half-time was evidenced according to the nature of the PLA matrix and the content of nanofillers. PMID:21623629

Goffin, Anne-Lise; Raquez, Jean-Marie; Duquesne, Emmanuel; Siqueira, Gilberto; Habibi, Youssef; Dufresne, Alain; Dubois, Philippe

2011-07-11

425

Synthesis, properties, and applications of composite materials based on grafted copolymers of perfluoropolymers and perfluorinated monomers with functional groups  

SciTech Connect

Statistic copolymers of tetrafluoroethylene and perfluorinated alkyl vinyl ethers (PFAVEFG) with functional groups are of wide application as membranes for chloro-alkali cells, fuel cells, etc., due to their unique properties of high thermal and chemical stability. These polymers are also used as catalysts for a wide range of organic reactions. Synthesis of the graft copolymers of PFAVEFG onto fluoropolymers would maintain the advantages of these catalysts while producing insoluble materials and decreasing expensive fluoro-monomer content without reducing the catalytic activity of the copolymers. The structure and catalytic properties of radiation induced graft copolymerization of perfluorinated alkyl vinyl ethers with sulfonyl fluoride (PFAVESF) were studied. Specific catalytic activity of the grafted copolymer was up to 40 times more than the same value for the statistic copolymer. Esterification of acrylic acid, alkylation of substituted phenol were also performed using the grafted copolymers.

Mislavsky, B.V.; Melnikov, V.P. [Institute of Chemical Physics, Moscow (Russian Federation)

1993-12-31

426

Aortic Replacement with Sutureless Intraluminal Grafts  

PubMed Central

To avoid the anastomotic complications and long cross-clamp times associated with standard suture repair of aortic lesions, we have implanted sutureless intraluminal grafts in 122 patients since 1976. Forty-nine patients had disorders of the ascending aorta, aortic arch, or both: their operative mortality was 14% (7 patients), and the group's 5-year actuarial survival rate has been 64%. There have been no instances of graft dislodgment, graft infection, aortic bleeding, or pseudoaneurysm formation. Forty-two patients had disorders of the descending aorta and thoracoabdominal aorta: their early mortality was 10% (4 patients), and the group's 5-year actuarial survival rate has been 56%. There was 1 early instance of graft dislodgment, but no pseudoaneurysm formation, graft erosion, aortic bleeding, intravascular hemolysis, or permanent deficits in neurologic, renal, or vascular function. Thirty-one patients had the sutureless intraluminal graft implanted in the abdominal aortic position: their early mortality was 6% (2 patients), and the 5-year actuarial survival rate for this group has been 79%. There were no instances of renal failure, ischemic complication, postoperative paraplegia, pseudoaneurysm, or anastomotic true aneurysm. Our recent efforts have been directed toward developing an adjustable spool that can adapt to the widest aorta or the narrowest aortic arch vessel; but in the meanwhile, the present sutureless graft yields shorter cross-clamp times, fewer intraoperative complications, and both early and late results as satisfactory as those afforded by traditional methods of aortic repair. (Texas Heart Institute Journal 1990; 17:302-9) Images PMID:15227522

Lemole, Gerald M.

1990-01-01

427

Adaptive significance of root grafting in trees  

SciTech Connect

Root grafting has long been observed in forest trees but the adaptive significance of this trait has not been fully explained. Various authors have proposed that root grafting between trees contributes to mechanical support by linking adjacent root systems. Keeley proposes that this trait would be of greatest advantage in swamps where soils provide poor mechanical support. He provides as evidence a greenhouse study of Nyssa sylvatica Marsh in which seedlings of swamp provenance formed between-individual root grafts more frequently than upland provenance seedlings. In agreement with this within-species study, Keeley observed that arid zone species rarely exhibit grafts. Keeley also demonstrated that vines graft less commonly than trees, and herbs never do. Since the need for mechanical support coincides with this trend, these data seem to support his model. In this paper, the authors explore the mechanisms and ecological significance of root grafting, leading to predictions of root grafting incidence. Some observations support and some contradict the mechanical support hypothesis.

Loehle, C.; Jones, R.

1988-12-31

428

Polymerization  

NSDL National Science Digital Library

In this activity, by the Concord Consortium's Molecular Literacy project, students "explore both polymers and copolymers." Upon completion of this activity students should be able to compare linear, branched, and cross-linked polymers; connect the density of polymers with differences in their structure; and connect polymer structures with their reversibility, and consider the importance for recycling." The activity itself is a java-based interactive resource built upon the free, open source Molecular Workbench software. In the activity, students are allowed to explore at their own pace in a digital environment full of demonstrations, illustrations, and models they can manipulate. In addition to the activity, visitors will find an overview of the activity, a test and rubric, central concepts, and their correlation to AAAS standards.

429

Treatment of stable vitiligo with autologous epidermal grafting and PUVA  

Microsoft Academic Search

Background: Previous reports have shown the benefits of epidermal grafting for vitiligo.Objective: Our purpose was to evaluate the effectiveness and complications of epidermal grafting in combination with PUVA on stable vitiligo refractory to conventional treatments.Methods: In 100 patients with stable refractory vitiligo we performed epidermal grafting with suction blisters followed by PUVA treatment. The grafted sites were examined for repigmentation

Seung Kyung Hann; Sungbin Im; Ha Wook Bong; Yoon-Kee Park

1995-01-01

430

21 CFR 870.3650 - Pacemaker polymeric mesh bag.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Pacemaker polymeric mesh bag. 870.3650 Section 870.3650 Food... § 870.3650 Pacemaker polymeric mesh bag. (a) Identification. A pacemaker polymeric mesh bag is an implanted device used to hold a...

2010-04-01

431

21 CFR 870.3650 - Pacemaker polymeric mesh bag.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Pacemaker polymeric mesh bag. 870.3650 Section 870